Guidelines for the echocardiographic studies of suspected subaortic and pulmonic stenosis.

INTRODUCTION

Subaortic stenosis (SAS) and pulmonic stenosis (PS) are, with PDA, the most common canine congenital heart defects in almost all epidemiological studies or frequency tabulations of the various European countries and the United States. As dog breeder's associations of highly affected breeds such as Boxers and Newfoundlands are attempting to screen breeding stock clinically as well as echocardiographically and are trying to eliminate these defects through the exclusion of affected individuals from breeding programs, it behooves the group of veterinary cardiologists and echocardiographers engaged in these screening programs to use a standardized approach to the echocardiographic examination procedure. This should warrant obtaining comparable studies with little interobserver variability due to the data acquisition procedure. Such uniformly acquired studies would also be easier to review by a board of experts, should this become necessary in the future. The recommendations stated below are valid for the examinations of dogs as well as cats. The present article represents the combined professional opinions of Drs. Bussadori, Le Bobinnec, Amberger and Lombard.

REQUIRED EQUIPMENT

Any commercial echocardiographic unit with 2.5 to 7.5 MHz sector transducers is suitable for imaging. Transducers with small "footprints" (contact surface) are easier to couple to the chest wall in small patients with narrow intercostal spaces. A so-called cardiac package is also required and provides the software for standardized M-mode, 2D- and Doppler measurements. An ECG-tracing must be included on all recordings. It is mandatory to record clear and artifact-free imaging sequences of adequate length of each required view and of each Doppler measurement on a videotape or digital archive system, with proper patient identification, for later retrieval and documentation. For the Doppler measurements, pulsed wave (PW) and continuous wave (CW) capabilities are required. Color flow Doppler (CFD) is a useful option and allows the rapid documentation and localization of turbulent blood flow, thereby facilitating the placement of the PWD- and CWD- cursors for spectral display and peak velocity measurements. It is however a costly option and not essential for the documentation of neither SAS or PS.

SEDATION

The authors highly recommend against tranquilization of the patients, as blood flow velocities are affected by most sedatives. Even if the blood pressure measured under sedation is in the normal range, this does not warrant truly non-influenced blood flow velocity values.