Angiographic Tool to Detect Pulmonary Arteriovenous Malformations in Single Ventricle Physiology

Abstract

Background: Individuals with single ventricle physiology who are palliated with superior cavopulmonary anastomosis (Glenn surgery) may develop pulmonary arteriovenous malformations (PAVMs). The traditional tools for PAVM diagnosis are often of limited diagnostic utility in this patient population. We sought to measure the pulmonary capillary transit time (PCTT) to determine its value as a tool to identify PAVMs in patients with single ventricle physiology.

Methods: We defined the angiographic PCTT as the number of cardiac cycles required for transit of contrast from the distal pulmonary arteries to the pulmonary veins. Patients were retrospectively recruited from a single quaternary North American pediatric center, and angiographic and clinical data was reviewed. PCTT was calculated in 20 control patients and compared to 20 single ventricle patients at the pre-Glenn, Glenn, and Fontan surgical stages (which were compared with a linear-mixed model). Correlation (Pearson) between PCTT and hemodynamic and injection parameters was assessed using 84 Glenn angiograms. Five independent observers calculated PCTT to measure reproducibility (intra-class correlation coefficient).

Results: Mean PCTT was 3.3 cardiac cycles in the control population, and 3.5, 2.4, and 3.5 in the pre-Glenn, Glenn, and Fontan stages, respectively. PCTT in the Glenn population did not correlate with injection conditions. Intraclass correlation coefficient was 0.87.

Conclusions: Pulmonary angiography can be used to calculate the pulmonary capillary transit time, which is reproducible between observers. PCTT accelerates in the Glenn stage, correlating with absence of direct hepatopulmonary venous flow.

Keywords: Pulmonary arteriovenous malformation; hepatic factor; pulmonary transit time; superior cavopulmonary anastomosis.

Figure 1:. Definition of the PCTT.

Pulmonary capillary transit time is defined as the number of cardiac cycles taken for contrast to traverse the pulmonary capillary bed. Calculation of the PCTT starts when the contrast reaches the distal major branches of the pulmonary arteries, and stops when the first visible contrast is present in the pulmonary veins.

Figure 2:. Loss of Direct Hepatopulmonary Blood Flow Leads to Reversible Acceleration of PCTT.

(A) There is no significant difference in the PCTT between patients with normal cardiopulmonary vascular connections and single ventricle patients in the Pre-Glenn or Fontan stage. However, the PCTT in patients with Glenn anatomy is significantly accelerated. (B) Tracking individual patients (from A) through each surgical stage shows accelerated PCTT in the Glenn that reverts to normal after restoration of direct hepatopulmonary blood flow. Two patients whose PCTT did not decrease from Pre-Glenn to Glenn are highlighted in red, and one patient whose PCTT did not increase from Glenn to Fontan is highlighted in blue. (C) Stage-to-stage difference for the individual patients shown in (B).