RHYTHM PUZZLE
Not so fast
...
TA. Simmers, A.M.W. Alings
Figure 1.
A n otherwise
healthy 37-year-old
woman was
Areferred with symptoms of palpitations. Physical
examination, laboratory work, cardiac ultrasound and 12-lead ECG were all within normal limits. Her family history was unremarkable. During routine treadmill TA. Shuman A.M.W. ANls Department of Cardiology, Amphia Hospital, Breda, the Netherlands
stress testing, she developed the arrhythmia in figure 1, with a precipitous drop in blood pressure. She remained conscious although in severe discomfort in a supine position. What is your (differential) diagnosis, what additional information do you need, and what is your next step? U
Answer You will find the answer on page 355.
Correspondence to: T.A. Simmers Department of Cardiology, Amphia Hospital, PO Box 90108, 4800 RA Breda, the Netherlands E-mail: [email protected]
#
Netherlands Heart Journal, Volume 14, Number 10,
October 2006
347
RHYTHM PUZZLE
Answer to the rhythm puzzle on page 347
Figure 1 shows a wide QRS complex tachycardia with a cycle length of 240 ms, i.e. 250 beats/min. It is a left bundle branch block pattern with a left axis; most striking is the absence of an R wave in all precordial leads. Differential diagnosis of any wide QRS tachycardia is either VT, SVT with aberrant conduction, or preexcitation. The latter is unlikely in this patient, as she had a normal resting ECG without manifest pre-excitation. Of the many algorithms for the interpretation of wide QRS tachycardia, that is to say to differentiate between VT and SVT with aberrancy, Figure 2. the most widely used is probably the one published by Brugada and coworkers in 1991.1 This algorithm allowed correct diagnosis of VT with a sensitivity of 98.7% and specificity of 96.5%. This impressive result was obtained with just three highly specific ECG characteristics of VT: AV dissociation, R-S nadir >100 ms in any precordial lead, and absence of Rin all precordial leads. The first is not easily assessable and not immediately apparent in this rapid tachycardia, the second is absent, but the third definitely applies. So the most likely diagnosis here is VT. In theory, carotid sinus massage or intravenous adenosine could be tried in case of Figure 3. doubt, or more invasively even introducing a temporary pacing lead both to assess possible AV dissociation and to overpace the arrhythmia. Given the patient's haemodynamic compromise, however, the most important measure is rapid cardioversion. Before this could be undertaken, the tachycardia suddenly decelerated as shown in figure 2 (where numbers indicate tachycardia cycle length). What is the diagnosis now?
J1
. ,
1
....... -...
_.
*..4;,..4...
The most striking feature of this strip is the fact that the tachycardia on the right is precisely halfthe speed of the original arrhythmia (from 250 beats/min and 240 ms to 125 beats/min and 480 ms). At the same time the QRS is narrower. This should immediately raise the suspicion of a transition from 1:1 to 2:1 conduction of a rapid SVT (i.e. atrial flutter); the 12lead ECG confirmed this suspicion (figure 3, where vertical scores in V1 denote P waves).
WE..-E ..4
V
still missing: the patient was on flecainide. Although combined with metoprolol in this patient, the flutter rate was slow enough due to the class Ic drug and AV conduction good enough in this young woman to temporarily allow 1:1 AV conduction under conditions of sympathetic drive (maximal exercise). ECG algorithms differentiating between VT and SVT with aberrant conduction were not derived from and are not applicable to patients on antiarrhythmic drugs. This case provides two valuable lessons: ECG diagnosis of wide QRS tachycardia may be deceptive in the presence of antiarrhythmic drugs, and patients starting treatment with a class I drug should routinely undergo stress testing to exclude proarrhythmia or phenomena such as seen in this patient. She has since undergone successful catheter ablation of atrial flutter, but is still on drugs due to concomitant paroxysmal atrial fibrillation. U Reference
So why did the ECG algorithm lead us astray in the first ECG? The clue to the answer lies in the relatively slow rate ofthe flutter, and is the one piece of information
qC
Netherlands Heart Journal, Volume 14, Number 10, October 2006
1
Brugada P, Brugada J, Mont L, et al. A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex. Circulation 1991;83:1649-59.
355
Not so fast
...
TA. Simmers, A.M.W. Alings
Figure 1.
A n otherwise
healthy 37-year-old
woman was
Areferred with symptoms of palpitations. Physical
examination, laboratory work, cardiac ultrasound and 12-lead ECG were all within normal limits. Her family history was unremarkable. During routine treadmill TA. Shuman A.M.W. ANls Department of Cardiology, Amphia Hospital, Breda, the Netherlands
stress testing, she developed the arrhythmia in figure 1, with a precipitous drop in blood pressure. She remained conscious although in severe discomfort in a supine position. What is your (differential) diagnosis, what additional information do you need, and what is your next step? U
Answer You will find the answer on page 355.
Correspondence to: T.A. Simmers Department of Cardiology, Amphia Hospital, PO Box 90108, 4800 RA Breda, the Netherlands E-mail: [email protected]
#
Netherlands Heart Journal, Volume 14, Number 10,
October 2006
347
RHYTHM PUZZLE
Answer to the rhythm puzzle on page 347
Figure 1 shows a wide QRS complex tachycardia with a cycle length of 240 ms, i.e. 250 beats/min. It is a left bundle branch block pattern with a left axis; most striking is the absence of an R wave in all precordial leads. Differential diagnosis of any wide QRS tachycardia is either VT, SVT with aberrant conduction, or preexcitation. The latter is unlikely in this patient, as she had a normal resting ECG without manifest pre-excitation. Of the many algorithms for the interpretation of wide QRS tachycardia, that is to say to differentiate between VT and SVT with aberrancy, Figure 2. the most widely used is probably the one published by Brugada and coworkers in 1991.1 This algorithm allowed correct diagnosis of VT with a sensitivity of 98.7% and specificity of 96.5%. This impressive result was obtained with just three highly specific ECG characteristics of VT: AV dissociation, R-S nadir >100 ms in any precordial lead, and absence of Rin all precordial leads. The first is not easily assessable and not immediately apparent in this rapid tachycardia, the second is absent, but the third definitely applies. So the most likely diagnosis here is VT. In theory, carotid sinus massage or intravenous adenosine could be tried in case of Figure 3. doubt, or more invasively even introducing a temporary pacing lead both to assess possible AV dissociation and to overpace the arrhythmia. Given the patient's haemodynamic compromise, however, the most important measure is rapid cardioversion. Before this could be undertaken, the tachycardia suddenly decelerated as shown in figure 2 (where numbers indicate tachycardia cycle length). What is the diagnosis now?
J1
. ,
1
....... -...
_.
*..4;,..4...
The most striking feature of this strip is the fact that the tachycardia on the right is precisely halfthe speed of the original arrhythmia (from 250 beats/min and 240 ms to 125 beats/min and 480 ms). At the same time the QRS is narrower. This should immediately raise the suspicion of a transition from 1:1 to 2:1 conduction of a rapid SVT (i.e. atrial flutter); the 12lead ECG confirmed this suspicion (figure 3, where vertical scores in V1 denote P waves).
WE..-E ..4
V
still missing: the patient was on flecainide. Although combined with metoprolol in this patient, the flutter rate was slow enough due to the class Ic drug and AV conduction good enough in this young woman to temporarily allow 1:1 AV conduction under conditions of sympathetic drive (maximal exercise). ECG algorithms differentiating between VT and SVT with aberrant conduction were not derived from and are not applicable to patients on antiarrhythmic drugs. This case provides two valuable lessons: ECG diagnosis of wide QRS tachycardia may be deceptive in the presence of antiarrhythmic drugs, and patients starting treatment with a class I drug should routinely undergo stress testing to exclude proarrhythmia or phenomena such as seen in this patient. She has since undergone successful catheter ablation of atrial flutter, but is still on drugs due to concomitant paroxysmal atrial fibrillation. U Reference
So why did the ECG algorithm lead us astray in the first ECG? The clue to the answer lies in the relatively slow rate ofthe flutter, and is the one piece of information
qC
Netherlands Heart Journal, Volume 14, Number 10, October 2006
1
Brugada P, Brugada J, Mont L, et al. A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex. Circulation 1991;83:1649-59.
355
