© 2014, Wiley Periodicals, Inc. DOI: 10.1111/echo.12625



Echocardiographic Evaluation of Patent Foramen Ovale and Atrial Septal Defect* Pawan Hari, M.D., Ramdas G. Pai, M.D., F.A.C.C., F.R.C.P. (Edin), and Padmini Varadarajan, M.D., F.A.C.C. Division of Cardiology, Loma Linda University Medical Center, Loma Linda, California

Patent foramen ovale (PFO) is a common variant present in up to 25% of the population. Atrial septal defect (ASD) is a direct communication between the 2 atrial chambers, of which the ostium secundum variety is the most common. This manuscript is an in depth review of the complex atrial septation, the diagnosis of PFO and ASD and its clinical and therapeutic implications. (Echocardiography 2014;00:1–15) Key words: atrial septal defect, echocardiography, patent foramen ovale

Introduction, Epidemiology, and Genetics: Atrial septal defect (ASD) is a direct communication between the 2 atrial chambers which allows shunting of blood. ASDs were first classified based on their morphology and location by Rokitansky (Fig. 1). Epidemiologically, secundum (60%) defects are the most common type of ASD followed by primum (20%), and sinus venosus (15%), and lastly the coronary sinus (CS) (8% drop in arterial saturation to 1.5:1 leads to RV volume overload and possibly increase in pulmonary vascular resistance (PVR). Irreversible increases in PVR and pulmonary hypertension are less common and develop much later in life than in ventricular septal defects and arterial-to-pulmonary communications. Symptoms: Patients with primum ASDs typically present in childhood, while other types of ASDs present later in life. Majority of children with isolated nonprimum ASDs are free of symptoms and may present with a heart murmur, while others are detected incidentally when referred for an echocardiogram for other reasons. Adults with ostium secundum ASDs start presenting during the 3rd or 4th decade usually with symptoms of fatigue or dyspnea on exertion. Some patients may present with palpitations as a result of atrial fibrillation or flutter secondary to atrial dilatation. Less commonly, patients may present with systemic emboli due to paradoxical embolization. Older patients may also present with frank right heart failure with associated severe tricuspid regurgitation (TR) secondary to right atrial/ventricular dilation and annular stretch. Pulmonary hypertension may occur secondary to severe 7

Hari, Pai and Varadarajan

volume overload. Eisenmenger physiology can lead to central cyanosis which may also be the presenting sign/symptom. Cyanosis occurs more commonly in the IVC type sinus venosus defect due to shunting of deoxygenated blood from the IVC through a prominent eustachian valve into the left atrium. Signs: Inspection: Phenotypic features of Down syndrome or Holt Oram syndrome are occasionally seen. Cyanosis is rare in patients with isolated ASDs. Central cyanosis points toward presence of an IVC type sinus venosus defect or associated pulmonic stenosis. Elevated jugular venous pressure (JVP) maybe present in the setting of right heart failure or TR secondary to annular stretch. Palpation: Right ventricular lift maybe palpated, especially during deep expiration. Auscultation: A wide and fixed split S2 is classically associated with ASD. A continuous flow through the venous confluence may produce a soft venous hum in the left upper sternal border. A relative tricuspid stenosis murmur due to increased flow through the right side of the heart may be heard as a diastolic rumble over the left lower sternal border. Pulmonary hypertensionrelated auscultatory signs such as TR murmur and a loud P2 may be heard. A mitral regurgitation murmur is heard when a primum ASD occurs in association with a cleft MV.

lel to the ultrasound beam, dropout can occur. This may lead to a false diagnosis of ASD. On the contrary, the subcostal four-chamber views allow better visualization of the atrial septum and some of the associated defects. Doppler echocardiography is useful in the diagnosis of ASD. Pulsewave Doppler at the level of the defect usually demonstrates a classic triphasic left-to-right shunt, characterized by flow waveforms in late systole and diastole, with a presystolic accentuation caused by atrial contraction (Fig. 14). The normal venous flow-pattern should be distinguished from an ASD flow-pattern. The venous pattern starts earlier in systole, has distinct systolic, diastolic, and atrial reversal waves and will usually increase with inspiration. Right-to-left or bidirectional flow develops in patients with high right atrial pressures resulting from RV diastolic dysfunction or significant TR. In a bubble study, left-to-right shunting can be identified as a negative contrast effect (Fig. 15). Increased pulmonary blood flow over a period of time causes pulmonary hypertension secondary to vascular remodeling. Color flow is used to visualize the actual shunt. Pollick et al.39 found a correlation between color jet width and left-to-right shunt size with echocardiography. In their study, a color flow width of 15 mm was suggestive of a Qp:Qs > 2:1. Qp:Qs ratio can also be used by continuity equation.40 Multiple views are recommended to ensure reproducibility in the calculation of right-sided cardiac output. Calculation of Qp:Qs in adults is difficult.41 Most of the error

Chest X-Ray: Cardiomegaly secondary to right atrial and right ventricular dilation if often noted. In patients with ostium primum ASDs, left-sided dilatation maybe present due to associated mitral regurgitation. In addition, prominence of the pulmonary trunk and proximal pulmonary branches maybe noted due to increased pulmonary blood flow. Echocardiography (Detection): Most of the ASDs are single and vary in size. These defects can be directly visualized using two-dimensional (2D) echocardiography. ASD is suspected when there is right ventricular dilatation in an otherwise healthy person. On M-mode, RV dilatation and abnormal septal motion are noted. Leftward septal motion in late diastole is characteristic of RV volume overload in cases with significant shunting. Multiple echocardiographic views are used to assess the presence, location, size, and hemodynamic impact of the shunt. In the apical four-chamber views, as the atrial septum is paral-


Figure 14. Shows calculation of flow across an ASD. TVI = 39 cm. Defect size 3.0 cm (radius is 1.5 cm). HR is 70 bpm. ASD flow/beat = 39 9 3.14 9 1.5 9 1.5 = 183 cc. 183 9 70 = flow/min. ASD = atrial septal defect.


Figure 15. A TEE image demonstrating “negative contrast effect” in the right atrium due to left-to-right shunting in a patient with secundum ASD. TEE = transesophageal echocardiography; ASD = atrial septal defect.

occurs in the calculation of cross-sectional area of the right ventricular outflow tract. Qp:Qs ratio is calculated as follows.42 Qp: Qs = (RVOT TVI 9 RVOT area)/(LVOT TVI 9 LVOT area) [RVOT = right ventricular outflow tract; TVI = time-velocity integral; LVOT = left ventricular outflow tract]. Shunt volume across an ASD can be calculating by calculating the area of the ASD, the time-velocity integral (TVI) of flow across the defect and the heart rate.43Shunt flow (cc/min) = ASD area (cm2) 9 ASD flow TVI (cm) 9 heart rate (Fig. 14). Patent foramen ovale detection similarly starts with color flow Doppler (CFD) of the atrial septum in multiple views. If CFD does not reveal an obvious shunt, it should be followed by intravenous injection of agitated saline. Early visualization (

Echocardiographic evaluation of patent foramen ovale and atrial septal defect.

Patent foramen ovale (PFO) is a common variant present in up to 25% of the population. Atrial septal defect (ASD) is a direct communication between th...
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