Echocardiographic Evaluation of Indices of Severity of Pulmonary Stenosis in Dogs: Reproducibility and Effects of General Anesthesia

Abstract

Background

The effects of general anesthesia (GA) on less flow-dependent (velocity ratio, velocity time integral [VTI] ratio and indexed pulmonary valve area [iPVA]) and flow-dependent (mean [PVmeanPG] and maximum pressure gradient [PVmaxPG]) indices of severity of pulmonary stenosis (PS) are unclear.

Objectives

Determine the effects of GA on indices of severity of PS in dogs undergoing an interventional procedure (IP). Determine the reproducibility of indices of severity of PS.

Animals

Thirty-nine dogs with PS.

Methods

Prospective cross-sectional study. Five repeated echocardiograms were performed over 3 days. Day 1: two echocardiograms were performed by 2 different operators. Day 2: echocardiograms were performed before and after GA but before IP. Day 3: an echocardiogram was performed after the IP.

Results

After GA, median (IQR) cardiac index (2.1 [1.6–2.6] L/min/m²), PVmeanPG (45.0 [26.0–55.2] mmHg), PVmaxPG (76.6 [46.6–100.3] mmHg) were decreased (p $\le 0$.001) compared to before GA (2.8 [2.2–3.0] L/min/m², 55.9 [47.6–73.1] mmHg, 96.1 [81.6–127.0] mmHg, respectively). There were no differences (p $\ge 0$.35) in velocity ratio, VTI ratio, or iPVA after GA. Intra-operator and inter-operator coefficients of variation (95% CI) were highest for iPVA (13.8% [10.4–18.4] and 13.5% [11.0–18.4], respectively) and lowest for velocity ratio (9.2% [7.7–12.3] and 9.3% [7.7–12.4], respectively).

Conclusions and Clinical Importance

PVmeanPG and PVmaxPG might be misleading in states of reduced flow. An integrative assessment of severity of PS that includes less flow-dependent indices is recommended. Reproducibility of indices of severity of PS should be considered when re-evaluating dogs with PS.