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Review

Atrial and ventricular tachyarrhythmias in military personnel Bonnie N Posselt,1 A T Cox,1,2 J D’Arcy,1,3 M Rooms,4 M Saba4 1

Defence Medical Services, Royal Centre for Defence Medicine, Birmingham, UK 2 Department of Cardiology, St George’s, University of London, London, UK 3 Department of Cardiology, RCDM (Oxford), John Radcliffe Hospital, Oxford, UK 4 Regional Occupational Health Team (North), Catterick Garrison, North Yorkshire, UK Correspondence to Flt Lt Bonnie N Posselt, RAF Henlow, Officers’ Mess, Hitchin, Befordshire, SG16 6DN; [email protected] Received 29 June 2015 Accepted 30 June 2015 Published Online First 5 August 2015

ABSTRACT Although rare, sudden cardiac death does occur in British military personnel. In the majority of cases, the cause is considered to be a malignant ventricular tachyarrhythmia, which can be precipitated by a number of underlying pathologies. Conversely, a tachyarrhythmia may have a more benign and treatable cause, yet the initial clinical symptoms may be similar, making differentiation difficult. This is an overview of the mechanisms underlying the initiation and propagation of arrhythmias and the various pathological conditions that predispose to arrhythmia genesis, classified according to which parts of the heart are involved: atrial tachyarrhythmias, atrial and ventricular, as well as those affecting the ventricles alone. It encompasses atrial tachycardia, atrial flutter, supraventricular tachycardias and ventricular tachycardias, including the more commonly encountered inherited primary electrical diseases, also known as the channelopathies. The clinical features, investigation and management strategies are outlined. The occupational impact—in serving military personnel and potential recruits—is described, with explanations relating to the different conditions and their specific implication on continued military service.

During a maximal effort assault course, a 20 year old Private is forced to stop due to sudden symptoms of rapid palpitations and pre-syncope. His symptoms persist for two minutes followed by spontaneous and immediate resolution. The soldier reports to his Regimental Medical Officer where, on questioning, he admits to similar episodes whilst running or undertaking strenuous exercise. He has no family history of sudden cardiac death. He drinks moderate alcohol, but occasionally binge-drinks at weekends. He takes no medication, denies illicit drug use, and is a non-smoker. On examination at rest his pulse rate is 54 beats per minute and regular. He is normotensive with no added heart sounds. A 12 lead ECG demonstrates normal sinus rhythm with a short PR interval of 80ms and a broad QRS complex with a slurred upstroke. A cardiology opinion is sought. In the meantime, he is downgraded to ‘unfit service outside base area’ and ‘unfit strenuous physical activity’ (JMES = MND Temp A4 L4 M4 E3).

Key messages ▸ Tachyarrhythmias range from being benign to life threatening and may have significant occupational implications to members of the Armed Forces. ▸ Understanding the arrhythmia mechanism and underlying pathology will guide appropriate management. ▸ Investigations should focus on assessing cardiac structure and function, including electrical and biochemical elements. ▸ Management is rhythm specific, ranging from lifestyle changes to pharmacological treatments and interventional therapies.

documented. Sudden death rates in recruits have been reported as varying from 2 to 13 per 100 000 recruit years1 2 and the majority result from underlying yet undetected cardiac abnormalities. In 86% of cases exercise participation was temporally associated with death.2 The most common underlying diseases that cause death are anomalous coronary artery origins and inherited cardiovascular disorders, such as hypertrophic cardiomyopathy (HCM) or long QT syndrome (LQTS). Regardless of the underlying pathology, the common terminal pathway leading to death is usually a ventricular tachyarrhythmia. Atrial tachyarrhythmias tend to have a more benign natural history, with distracting symptoms far more common than disabling or fatal symptoms. Accessory pathways are the notable exception, as when atrial fibrillation (AF) is superimposed, they can present with sudden death in a minority of patients. Regardless of the arrhythmia there are symptoms common to tachyarrhythmias in general, even as the underlying mechanisms and implication on continued military service differ significantly. This article summarises the mechanisms, management and clinical features of atrial and ventricular tachyarrhythmias, with particular emphasis on the resulting occupational impact on military personnel. An overview of all the tachyarrhythmias covered can be seen in Table 1.

INTRODUCTION

To cite: Posselt BN, Cox AT, D’Arcy J, et al. J R Army Med Corps 2015;161: 244–252. 244

Any unexpected death in a young person is always a tragedy and, in this respect, military personnel are no different to their civilian counterparts. Indeed while servicemen and women appear to be paragons of health and fitness, in fact, cases of sudden death, although uncommon, are well

MECHANISMS OF CARDIAC ARRHYTHMIAS Arrhythmias are caused by three mechanisms: spontaneous automaticity, triggered activity and re-entry circuits, the first two of which are related to abnormal impulse generation and the latter to abnormal impulse conduction.

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Review Table 1 An overview of tachyarrhythmias, presenting symptoms, ECG findings and treatment options Anatomical classification

Subclassification

Common symptoms

ECG pattern

Treatment

Atrial

Atrial flutter

Palpitations Presyncope

Saw-tooth baseline pattern

Atrial fibrillation

Palpitations Presyncope Fatigue Palpitations Chest pain Presyncope Palpitations Chest pain Presyncope

Undulating baseline and irregular ventricular rate

Antiarrhythmics DC cardioversion Catheter ablation Antiarrhythmics DC cardioversion Catheter ablation Vagal manoeuvres Adenosine Catheter ablation Antiarrhythmics (eg, flecainide, propafenone) Catheter ablation

SCD Palpitations Type 1—induced by exercise and swimming Type 2—induced by emotion and stress Type 3—occurs on waking suddenly SCD Palpitation Presyncope SCD Palpitations

QTc > 440 ms in men, >460 ms in females Torsades de pointes

Correct electrolyte imbalance Stop causative medications Lifestyle advice Genetic testing ICD

Normal resting SR. VT induced on exercise

β-blockers Genetic testing ICD Genetic testing Quinidine ICD

Atrial and ventricular

AVNRT

AVRT

Ventricular Normal structure anatomy

Long QT syndrome

Catecholaminergic polymorphic pentricular tachycardia (CVPT) Brugada

RVOT-VT

Palpitations Presyncope

Fascicular

Palpitations Presyncope

Narrow QRS tachycardia

Pre-excitation (delta wave) Narrow QRS tachycardia in Orthostatic AVRT. Broad QRS in antidromic AVRT.

Type 1—broad QRS with coved ST and negative T wave Type 2—broad QRS with saddleback ST and positive or biphasic T wave Type 3—broad QRD with saddleback ST, positive T wave Broad regular QRS May show LBBB with right axis deviation. Occurring during exercise Normal resting SR Broad regular QRS May show RBBB with left axis deviation

Vagal manoeuvres Antiarrhythmics β-blockers Catheter ablation CCB or β blockers Antiarrhythmics Ablation of re-entry circuits

AVNRT, atrioventricular nodal re-entrant tachycardia; AVRT, atrioventricular re-entrant tachycardia; CCB, calcium channel blocker; DC, direct cardioversion; ICD, implantable cardiac defibrillator; LBBB, left bundle branch block; RBBB, right bundle branch block; RVOT, right ventricular outflow tract; SCD, sudden cardiac death; SR, sinus rhythm; VT, ventricular tachycardia.

Cardiac cellular automaticity is the first type of arrhythmia mechanism and is the spontaneous generation of an electrical impulse during phase 4 depolarisation of the action potential. This is also the mechanism underlying the normal cardiac cycle, which is initiated in the sinoatrial node (SA), transmitted through atrial myocytes to the atrioventricular node, before being propagated to the ventricular myocardium via the His–Purkinje system. The discharge rate of the SA node usually exceeds that of all other myocardial cells and thus suppresses their individual automaticity. The chronotropic effect of sympathetic innervation is an example of normal automaticity. The key feature of automaticity is that it is truly spontaneous and does not rely on any prior electrical activity. Pathological automatic impulses can be generated in the presence of inflammation or scar tissue; damaged cells have a higher (less negative) membrane potential, predisposing them to premature spontaneous discharge. The second mechanism of arrhythmia genesis is triggered activity, derived from an electrical impulse that has been directly generated from a prior impulse. In the repolarisation phase there are depolarising oscillations preceding the action potential that will generate a new impulse in the myocardium if they exceed a certain threshold. A number of different conditions can predispose to these after-depolarisations, thought to result from an overload of calcium in the myoplasm.3

Re-entry is the third and most common mechanism for clinical arrhythmias and is an abnormality in the propagation of an electrical impulse; instead of vanishing spontaneously it is recirculated, creating repetitive excitation. Typically there is a central area or obstacle that blocks the impulse, around which it is diverted. The core of non-conductive tissue could include the fibrous atrioventricular annulus or scarring of the myocardium itself. Clinically, tachycardia can be defined as physiological or pathological. Those that are physiological include the sinus tachycardia of anxiety or that generated as a response to exercise, though they might also be due to a systemic pathology such as hyperthyroidism or infection. Pathological re-entry tachyarrhythmias may have a circuit that includes the atria only, both atria and ventricles or the ventricles alone. If the arrhythmia lasts longer than 30 s, or is associated with symptoms of hypoperfusion, it is described as sustained. Understanding the underlying mechanism, and—in the case of re-entry—the conduction pathway, is key to managing the arrhythmia. The atrial only tachyarrhythmias, known collectively as supraventricular tachycardias (SVT), include AF, atrial flutter, atrial tachycardia (AT) and atrioventricular nodal re-entry tachycardia (AVNRT). AF is the most common sustained atrial tachyarrhythmia and is discussed elsewhere in this edition.4 An additional SVT is the atrioventricular re-entry tachycardia

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Review (AVRT), seen when an accessory pathway, additional to the atrioventricular (AV) node, conducts between the atria and ventricles and it has a conduction pathway that involves both atria and ventricles. Ventricular tachycardia (VT) circuits involve ventricular tissue only.

medical board has the health of the concern. Additionally, the broader risk military operation, the operational and vices and the reputational, political assessed by the medical board.

CLINICAL FEATURES

SUPRAVENTRICULAR TACHYCARDIAS

The military patient may present in a number of different ways. It may be that an abnormality is detected on the ECG of an asymptomatic serviceman or woman during a medical examination for another reason, that is, a screening medical or a preoperative assessment, or it may be that they exhibit symptoms suggestive of cardiac disease. Each individual requires detailed questioning for any history of possible cardiac symptoms, including palpitations, presyncope, syncope, exertional chest pain or dyspnoea. Palpitations that start and terminate suddenly are more suggestive of a pathological arrhythmia than those of a slow onset and offset. Patients are often able to tap out the rate and rhythm of their palpitations with their finger. Syncope occurring at rest and when lying down is more suspicious than on standing, when other mechanisms such as neurocardiogenic syncope or orthostatic hypotension are more commonly seen than a serious arrhythmia. Most tachyarrhythmias will present with one or more of these symptoms that in general are nonspecific for a particular tachyarrhythmia. The exception to this rule is syncope, which occurs more commonly in VTs than SVT. An overlap between epilepsy and ventricular tachyarrhythmias has been observed; this may relate to an overlap in the underlying pathology or more likely a misdiagnosis.5 Use of prescription or recreational medications must be ascertained; potentially important drugs include those that might prolong the QT interval or be cardiotoxic. A detailed pedigree must also be elicited, particularly searching for any history of sudden cardiac death or disability from cardiac disease in relatives under 50 years of age. Generic investigations generally include a 12-lead ECG, ambulatory monitoring with a Holter, an event monitor or implantable loop recorder. Exercise stress testing can be useful to provoke arrhythmias. Imaging with echocardiography is a first-line investigation, but cardiac MRI or CT may identify particular structural abnormalities that may be responsible for the genesis of the arrhythmia. The nature of military service means the service person can be called for duty at any time and even when training in the UK, Europe or USA, the service person can be remote from the normal provision of prehospital and secondary care services. The initial occupational health action is to ensure that the employer, the Chain of Command (CoC), is advised to keep the patient available for investigation and treatment, and within the normal reach of prehospital emergency care services by means of a temporary Joint Medical Employment Standard ( JMES). Generally, that will mean advising against operational deployment (medically non-deployable (MND)), advising against flying or aircraft-controlling duties (A4), advising against full duties in the ‘Land’ environment (L3 or L4 depending on the restrictions to trade duties), advising against embarkation (M3 if able to carry out duties on a ship in harbour or M4 if onshore duties only) and advising against travel outside of the UK (E3). When the aetiology, treatment options and outcomes are known, a medical grading can be awarded that will describe to the CoC the recommended employment options at an acceptable level of risk. As medical boards advise the CoC of the specific service, the medical board is itself constituted with an occupational medicine consultant from the same service. The

The incidence of SVT is estimated at 35/100 000 person-years with a prevalence of 2.23/1000 persons.6 Aside from AF there are four main types: AT, atrial flutter, AVNRT and AVRT and although these differ in their underlying mechanisms, their overlapping syndrome of predominantly palpitations and dizziness usually evades clinical differentiation. The AV node sits between the atria and the ventricles, where it transmits the electrical impulse generated by the SA node to the His–Purkinje ventricular system. The AV node is critical to both AVNRT and AVRT re-entry circuits. It is constituted of a discrete area of specialised conducting tissue that slows down the electrical impulse, thus allowing the atria to have fully contracted and filled the ventricles, before ventricular systole occurs. The AV nodal tissue is unique in the heart as the more frequently the AV node is stimulated, the slower the AV node transmits impulses to the ventricle. This characteristic, known as decremental conduction, acts as a limiter to the maximum rate of transmission through the AV node. The rate at which AV conduction block occurs varies between individuals and is dependent of the autonomic tone of the individual at the time of testing.

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patient as its primary to other personnel, the evacuation medical serand financial risk are

Atrial tachycardia AT encompasses both focal and re-entrant arrhythmias. Focal AT results from discrete areas of myocardium within the atrium, which have abnormal automaticity and are activated independently of the SA node, or harbour a microreentrant circuit. The electrical conduction spreads out centrifugally, propagating electrical current throughout the myocardium. Typical foci occur most commonly around the crista terminalis7 but also around the tricuspid annulus, right atrial appendage and pulmonary veins.8 Ectopic AT has been found to have a prevalence of 0.34% in asymptomatic individuals and 0.46% in those who report symptoms such as palpitations, dizziness, dyspnoea, fatigue and syncope.9 In contrast to other SVTs, there is an equal predominance of AT between the sexes. On the whole, AT is a benign disorder with spontaneous cessation seen in 55% of those patients under 25 years, reducing to 16% in those over 26 years of age.10 Only in rare cases of persistent AT may a patient go on to develop a tachycardia-induced cardiomyopathy.11 It can be difficult to differentiate AT on ECG findings alone. There is a narrow complex tachycardia, which can be paroxysmal, with an abnormal P wave axis or morphology being the only subtle clue occasionally seen—as such, a diagnosis is usually made with electrophysiological (EP) studies.8 Pharmacological treatment has limited efficacy whereas catheter ablation is a highly effective form of treatment and is preferentially used. Success rates have been reported as being >90%,12 with low recurrence rates of around 5% at 18 months.13 Catheter ablation consists of destructive energy applied directly to the myocardial tissue via ablation catheters inserted percutaneously under local anaesthetic. The radiofrequency current generates heat, causing necrosis of the underlying tissue; extreme cold (cryoablation) works similarly. This strategically placed and intentional scar disrupts the aberrant conduction pathways, preventing onward propagation of the arrhythmia.

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Review

Figure 1 ECG extract of atrial flutter taken from lead 2. Atrial activity marked by the red arrows illustrates the ‘saw-tooth’ baseline.

Atrial flutter

Atrial flutter is a paroxysmal re-entry circuit arrhythmia typically located in the right atrium, manifesting on the ECG as a fast, regular tachycardia, with a ‘saw-tooth’ baseline pattern (Figure 1). In typical atrial flutter, an impulse travels in an anticlockwise direction up the atrial septum, across and down the lateral wall of the right atrium, that is, the circuit propagates in a loop around the tricuspid valve, anterior to the crista terminalis and inferior vena cava. Less commonly, impulses travel in a clockwise direction, a variant of typical atrial flutter—both forms are termed cavotricuspid isthmus-dependent atrial flutter. Atrial flutter is normally a paroxysmal arrhythmia, lasting seconds to hours and commonly results in the symptoms of palpitations, reduced exercise tolerance and presyncope. The effect of decremental conduction through the AV node is commonly seen limiting the ventricular rate in atrial flutter. For example, the ventricular rate on the ECG may be 150 bpm while the atrial rate might be 300 bpm. This lower ventricular rate occurs due to the decrementing AV node blocking half the depolarisation events that stimulate it. Depending on the clinical presentation, atrial flutter can be terminated with antiarrhythmic medication or direct current cardioversion;14 both are highly successful methods of restoring sinus rhythm, but recurrence rates of 55% have been reported at 6 months.15 As the circuit is dependent on the myocardial tissue between the IVC and the tricuspid annulus, the long-term treatment of choice is catheter ablation of this tissue, with cure rates as high as 95%.16 Occupational restriction is indicated during the assessment and treatment process of both AT and flutter. In common with other arrhythmias, following successful ablation of atrial flutter, a return to employment duties is staged using time as the predictor of long-term health. For example, the Royal Air Force specifies a period of limitation of 2 years post ablation, without medication and in sinus rhythm before advising the CoC that the service person is normally employable; for those in high-risk roles such as pilots, a return to unlimited flying will not be possible.

Atrioventricular nodal re-entrant tachycardia The AV nodal tissue is located in the triangle of Koch bounded by the tricuspid annulus, the tendon of Todaro and the coronary sinus in the right atrium (Figure 2).

Figure 2 Diagram representation of the triangle of Koch located in the right atrium. Course of anterior fast tract and posterior slow tract illustrated with green and red arrows respectively. AV, atrioventricular.

Approximately 1% of the population have two conduction pathways within this area, an anterior, fast-conducting tract running along the tendon of Todaro and a posterior, slowconducting tract.17 It is thought that this dual-nodal physiology is congenital with incomplete symptom penetrance; only 65% of those with dual-nodal physiology go on to develop an arrhythmia.18 In addition, those patients that do develop AVNRT usually present in early adulthood as the AV node matures19 and are more likely to be female.18 In the typical form of AVNRT (90% of cases) the initial impulse is conducted down the slow tract before returning via the fast one and then continuing back down the slow pathway (Figure 3), thus completing the circuit and propagating a tachyarrhythmia. Symptoms coincide with episodes of SVT where the ECG will demonstrate a narrow QRS complex (120 ms). If each beat appears the same, it is monomorphic, indicating that the circuit is following the same pathway each beat.

Polymorphic VT When VT exhibits a varying QRS morphology and axis, it is labelled polymorphic VT. ‘Torsades de pointes’ is a form of polymorphic VT, where there is variation from beat to beat in its appearance, occurring in cases with a prolonged QT interval. It also has features of VF such as varying rate and QRS amplitude, yet the patient usually retains consciousness. It can be selfterminating, but it can also degrade into VF with complete loss of cardiac output and ultimately death. Polymorphic VT should be treated immediately with electrical cardioversion if there is evidence of haemodynamic compromise,27 and correction of

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Review any underlying electrolyte abnormalities and discontinuation of any medications that may prolong the QT interval.

Structurally abnormal hearts In a structurally abnormal heart, the most common underlying pathology causing VT is the healed postmyocardial infarction scar caused by ischaemic heart disease. The scar tissue can act as a substrate for re-entrant VT, due to the abnormal, slow conduction of the still surviving myocardial channels within the scar and its borders and may also provide the trigger for re-entry in the form of spontaneous ventricular ectopy from the scar border. Scar-dependent VT associated with ischaemic heart disease is not typically precipitated by acute ischaemia and frequently presents years after a healed myocardial infarction. In cases with superimposed acute ischaemia, the management should focus on restoring and maintaining normal rhythm and also on restoring blood flow. This can be done through medical therapy, percutaneous coronary intervention or surgery. Long-term management can comprise antiarrhythmic drug therapy, substrate ablation and in the case of VT associated with heart disease, an implantable cardiac defibrillator (ICD). In the younger military population, the most common causes of VT in the setting of a structurally abnormal heart are HCM, myocarditis and anomalous coronary arteries;2 26 other rarer causes include cardiac sarcoid, arrhythmogenic right ventricular cardiomyopathy (ARVC) and congenital structural abnormalities. All of these conditions are associated with VT and are triggered by abnormalities in the myocardial substrate. Predominantly, these conditions are treated by managing the underlying disease itself, but may be supplemented with antiarrhythmic medication, invasive EP studies with catheter ablation or even ICD implantation. With all forms of cardiomyopathy, there is a risk of progressive haemodynamic deterioration and sudden death and these conditions remain a contraindication to military enlistment. Serving personnel with these conditions must be under the care of a cardiologist and limited to ‘unfit service outside base areas’ (MND) and ‘unfit strenuous physical exertion’. Conditions with a risk of tachyarrhythmia are incompatible with flying duties and solo flight-controlling duties.21

Structurally normal hearts In those with no evident abnormality on ECG, 80% of VTs are idiopathic and induced by exercise.28 They arise commonly from the right ventricular outflow tract (RVOT) and are most likely to occur at the peak intensity during exercise or within 3–5 min of recovery.29 On the ECG the QRS will have a left bundle branch block morphology and an inferior axis with atrioventricular dissociation (Figure 6). Exercise induces catecholamine release and an increased sensitivity to these hormones is thought to be the trigger for the VT. In addition, during exercise potassium is released from the exercising muscles and this fluctuation may contribute to myocyte instability.30 Presenting symptoms are predominantly of palpitations but dizziness and syncope can also occur. Usually RVOT-VT is benign, sudden cardiac death is rare and spontaneous cessation can be seen in 5%–20%.20 The diagnosis of RVOT-VT is one of exclusion, and it is imperative that the patient is suitably investigated to rule out any underlying structural heart disease, coronary artery disease or electrolyte imbalance. As RVOT-VT is commonly catecholamine induced, it may respond to vagal manoeuvres, as described earlier, or a verapamil intravenous bolus. It is generally inadvisable to use adenosine in wide-complex tachycardia, but it may terminate 250

Figure 6 Comparison ECG lead 2 of right ventricular outflow tract-ventricular tachycardia (RVOT-VT) and fascicular VT. RVOT-VT. In the long term, RVOT-VT can be managed medically with β-blockers or calcium channel blockers with efficacy rates of 25%–50%.20 In the Armed Forces, catheter ablation is required to prevent episodic symptoms and allow unrestricted employment. Success rates with ablation are as high as 90% in experienced centres.20 As the right ventricle is a thin-walled structure, a potential complication of the procedure is perforation of the ventricle itself, although this is rare. The second main form of idiopathic VT originates from the left posterior fascicle and is termed fascicular VT and is much more prevalent in males. The most likely underlying pathology is of a localised re-entry circuit within the posterior Purkinje fibres; there is activation of bystander Purkinje fibres allowing retrograde conduction within the network of conducting fibres.31 Presenting symptoms would again be palpitations and occasionally syncope. During VT the ECG may show a right bundle branch block with left axis deviation morphology and is usually sinus rhythm (Figure 6). Imaging shows a structurally normal heart and other investigations are normal. In general, the risk of sudden cardiac death is rare and remission often occurs spontaneously. This subtype of VT typically responds to an intravenous bolus of the calcium channel blocker verapamil. It has thus been labelled ‘verapamil-sensitive’ idiopathic left ventricular VT. Catheter ablation can be performed, by mapping the mid-distal left ventricular septum and finding the earliest Purkinje potential activation during VT, with success rates of up to 90%.32 Following presentation and during investigation and treatment a temporary limitation is required. Follow-up of ablation will allow a reduction in employment limitations which is less prolonged than the follow-up required for conservative management. Where a choice of treatment exists between ablation and symptomatic treatment, the patient must be counselled to make the decision based on clinical risks rather than any effect downgrading may have on their career.

CHANNELOPATHIES Long QT syndrome The LQTS is a group of inherited disorders characterised by dysfunctional myocardial electrolyte channels that result in delayed ventricular repolarisation, seen on the ECG as prolongation of the QT segment. A prolonged QT interval of >440 ms in men and >460 ms in women is considered

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Review abnormal.33 However, a proportion of ‘silent’ carriers will have a normal QTc at rest,34 depending on the degree of penetrance. In cases of a borderline QTc an exercise stress test may reveal the abnormality to aid diagnosis, as the QT interval is not able to appropriately shorten with the increase in HR.35 Those who are affected by LQTS are predisposed to ‘Torsades de pointes’ and the potential adverse clinical deterioration that accompanies it. Prevalence is estimated at 1:5000.36 There are three more common and many rare types of LQTS, classified by their specific gene mutations. Types 1 and 2 are caused by defects in myocardial potassium channels, resulting in a decrease in outward potassium current whereas in type 3 there is an inward leak of sodium ions through abnormal sodium channels. The three most common forms are commonly described as presenting with typical symptoms, though in reality there is a significant overlap. The LQTS type 1 arises from a mutation in chromosome 11 and accounts for 42% of all cases.37 Factors that stereotypically trigger arrhythmic episodes are exercise and swimming. The LQTS type 2 results from a chromosome 7 mutation and patients most typically present with symptoms induced with emotion, stress and sudden noises. The less common LQTS type 3, accounting for 8% of cases,24 is associated with a defect in chromosome 3 and symptoms can occur on waking from sleep and deaths typically occur during sleep. A history of prior syncope is an adverse prognostic factor and an important predictor of events.38 A careful drug history must be obtained, as various drugs can prolong the QT interval including over the counter antihistamines, certain antibiotics, antiarrhythmics, antimalarials and psychiatric medications.39 The ECG is the first line of investigation, as LQTS can be diagnosed by detecting a prolonged corrected QT interval. In the case of a borderline QT interval, there is a spectrum of major and minor clinical features, such as a family history and congenital deafness, which aid in making a diagnosis.33 As the QT interval lengthens, there is an exponential increase in the risk of cardiac events with a 2.2-fold increase when QTc=600 ms.40 Particular genetic variants are associated with increased risk, such as the autosomal recessive Jervell and Lange-Nielsen syndrome or mutations in the cytoplasmic loops of LQTS1,41 and formal risk stratification is the domain of specialist inherited cardiac condition clinics. The management aims of LQTS are to reduce the risk of cardiac death. First-line management are lifestyle changes, with emphasis on avoidance of triggering factors including refraining from competitive sports. Treatment with β-blockade is indicated in most patients with LQTS, including those that are ‘gene positive, phenotype negative’, unless contraindicated due to another complaint (ie, asthma). Avoidance of medications that might prolong the QT interval should be ensured. In high-risk cases treatment includes the implantation of a cardiac defibrillator. The diagnosis of LQTS is not compatible with entry to the military and a medical board will detail the level of limitations required for safe employment but this often falls below the threshold of the employment board’s consideration of continued employment.

Catecholaminergic polymorphic ventricular tachycardia An inherited arrhythmia syndrome, catecholaminergic polymorphic ventricular tachycardia has a prevalence estimated at 1:10 000,42 but as the ECG is normal at rest accurate figures are elusive. Patients are usually preadolescent, but invariably in their first four decades, with syncopal events and a structurally normal heart when they present.43 The key feature is that the arrhythmia is highly reproducible with exercise testing, or on catecholamine

infusion. The mutated genes code for proteins responsible for the release of calcium from the sarcoplasmic reticulum, most commonly the ryanodine receptor. β-blockers, specifically nadolol, are the mainstay of treatment. Lifestyle changes, including avoidance of exercise and stressful environments, are also key to management.44 An ICD may be required in severe case uncontrolled with medical therapy and lifestyle changes. The disease is not compatible with military service and will prevent the recruit from taking part in any exercise testing. Serving personnel will be significantly restricted and limited from taking part in any physical training. Most medical and employment boards will regard this as grounds for medical discharge.

Brugada syndrome Brugada syndrome is an inherited genetic disease that commonly presents with VF and sudden cardiac death. It has an incidence of approximately 0.14%, and is predominantly seen in males (male: female ratio is 9:1), particularly of south east Asian origin.45 Patients often have abnormal sodium ion channel function that adversely affects the cardiac action potential. Recent data suggests an electrical abnormality localised to the RVOT, with slow impulse propagation, acting as a substrate for VF. Brugada syndrome has a diagnostic morphology on the ECG with a pseudo-right bundle branch block and coved-type ST elevation in the right precordial leads. The typical ECG morphology usually occurs transiently and the resting ECG is frequently normal. When the disease is suspected due to sudden death in the family or an aborted cardiac arrest, for example, the typical Brugada morphology may be unmasked using a class IA antiarrhythmic such as flecainide or ajmaline. These drugs themselves may cause tachyarrhythmias and should only be administered in specialist clinics with immediate access to resuscitation facilities. Approximately 20% of patients experience arrhythmias that typically occur at rest and during sleep or during a febrile episode. Definitive diagnosis can be made with genetic testing when a mutation of the sodium coding gene, SCN5A, is most commonly found (in 25%–30% of cases), but in most cases no mutation is identified. Testing for other genes coding for sodium channels is not widely available. Cardiac imaging is normal, although subtle changes such as localised inflammation and fibrosis may be seen, similar to the early stages of ARVC, from which it must be differentiated. Lifestyle changes to reduce risk include not eating large meals, particularly immediately before sleeping, controlling fevers and not drinking alcohol to excess, all of which are associated with an increased risk of adverse events. Particular medications that might aggravate the syndrome should also be avoided.46 No medical treatment is proved to reduce risk though quinidine may be useful;47 the only intervention proved to improve survival is insertion of an ICD.48 As such, Brugada syndrome is not compatible with recruitment to military service. The imposition of restrictive lifestyle changes, including that of alcohol moderation, by a medical board may require recommendation for medical discharge; an ICD will also impose limitations to military employment such as embarkation, operational deployment and service outside of base areas but an employment board has greater latitude in retaining the service person. Other primary electrical diseases are known, including the short QT syndrome, the early repolarisation syndrome and idiopathic VF. All are rare and their natural history is not yet well defined.

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Review With these results the patient undergoes invasive EP testing that reveals a right-sided accessory pathway. He undergoes uncomplicated radio frequency catheter ablation to the accessory pathway under a local anaesthetic. Cardiology followup at six months is unable to demonstrate pre-excitation or arrhythmia and he remains asymptomatic. At an occupational medical board review he is returned to full unrestricted military duties in a grade of MFD A4 L2 M1 E1.

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CONCLUSION

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Although rare, unexpected sudden death can occur, and indeed has occurred, in British military personnel. The causes of these deaths are most commonly cardiac in origin, with ventricular tachyarrhythmias usually being the common terminal pathway leading to death. An even greater level of morbidity occurs due to tachyarrhythmias that produce troublesome and potentially progressive symptoms over time. Affected individuals may be asymptomatic or present with clinical symptoms that should be taken seriously, resulting in referral for thorough investigation, as the clinical and occupational outcome can differ significantly, depending on the underlying condition. Clinicians should understand that a normal ECG at rest does not exclude a serious underlying pathology and if the presenting symptoms are suspicious then a referral to a cardiologist should be sought. Many abnormalities have high rates of resolution with ablative treatments, rendering future risk at near population norms; single service occupational physicians, with data from the cardiologist on risk of future events and care requirements, are best placed to advise on continuing employment, which in many cases will be with few or no limitations. Correction notice This article has been corrected since it was published Online First. The order of the authorship has been changed.

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Contributors The concept of this paper was initially developed by ATC. As the first author, I have written the bulk of the article and all references. ATC has helped me develop and expand upon certain sections. All other authors have reviewed the paper and added their specialised comments.

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Competing interests None declared.

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Provenance and peer review Commissioned; internally peer reviewed.

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Posselt BN, et al. J R Army Med Corps 2015;161:244–252. doi:10.1136/jramc-2015-000494

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Atrial and ventricular tachyarrhythmias in military personnel Bonnie N Posselt, A T Cox, J D'Arcy, M Rooms and M Saba J R Army Med Corps 2015 161: 244-252 originally published online August 5, 2015

doi: 10.1136/jramc-2015-000494 Updated information and services can be found at: http://jramc.bmj.com/content/161/3/244

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Atrial and ventricular tachyarrhythmias in military personnel.

Although rare, sudden cardiac death does occur in British military personnel. In the majority of cases, the cause is considered to be a malignant vent...
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