1350139 - High Qp:Qs in an isolated PAPVD; physiological impact of high left atrial pressure from longstanding aortic coarctation

Description of Clinical Presentation: An asymptomatic and previously healthy 12 year old male was referred for cardiology assessment due to a persistent murmur. On examination, he had reduced femoral pulses, a systolic ejection murmur at the LSB, and a systolic murmur at the subscapular area. The ECG showed right ventricular hypertrophy. Echocardiogram showed a dilated RA and RV with normal systolic function, with an estimated RVSP of 48 mmHg + RA pressure, based on mild TR. No ASD was present; however, the RUPV could not be well seen. There was a non-stenotic and non-regurgitant bicuspid aortic valve, and a suspicion was raised for coarctation as the aortic arch could not be seen clearly.

Diagnostic Techniques and Their Most Important Findings: A contrast enhanced cardiac MRI (1.5T) was performed confirming the suspicion of RUPV PAPVD and a moderate coarctation (Figure 1). The upper and middle pulmonary veins joined together, draining into the SVC posteriorly below the innominate vein junction (Figure 1 & 2). The RV was significantly dilated (RVEDVi 180 ml/m2) with preserved EF (62%). The LV size and function was normal, with subjective mild LVH but normal myocardial mass (Figure 3). Phase contrast imaging revealed a Qp:Qs = 2:1, with RPA:LPA relative flow of 68:32%. Estimated flow in the anomalous vein, based on SVC flow above and below the insertion, was 3.4 L/min/m2, approximately 48% of Qp. A staged surgical and catheterization approach was preferred by the family, for the PAPVD and coarctation respectively, and at the time of the catheterization, the LVEDP was 20 mmHg in the setting of an arch gradient of 30 mmHg, PA systolic pressure of 27 mmHg (Mean of 19 mmhg), with an RVEDP of 9 mmHg.

Learning Points from this Case: The high Qp:Qs in this case of a single anomalous pulmonary vein is surprising, as in most patients with single vein PAPVD and no additional shunts the Qp:Qs is low and rarely require intervention (1). In this case the chronic left heart obstruction led to increased
left-sided diastolic pressures, which would be transmitted to the normally connected veins, while the anomalous vein would see the lower SVC/RA pressure. Flow from the PA into those lung segments would be favored, accentuating the degree of left-to-right shunt,
which is reflected in the preferential RPA flow at CMR. Thus, an isolated single anomalous pulmonary vein in association with left heart obstructive lesions may lead to a significant degree of shunting.