The influence of anesthesia with isoflurane on the pulmonary and aortic blood flow of Racing Pigeons (Columba livia f. domestica) measured by pulsed wave Doppler echocardiography

Influence of anesthesia with isoflurane on myocardial velocities of racing pigeons (Columba livia f. domestica)

OBJECTIVE

Tissue Doppler imaging (TDI) is a new technique to measure the myocardial velocities of the avian heart. Using this technique, the present study investigated the influence of isoflurane anesthesia on the systolic and diastolic longitudinal myocardial velocities in racing pigeons.

MATERIAL AND METHODS

Racing pigeons (n = 40) were anesthetized with isoflurane with a semi-open anesthesia system with an anesthetic mask and spontaneous breath. The echocardiographic examination was performed during the stage of surgical anesthesia with the failure of the toe pinch and wing twitch reflexes and with deep regular breaths. Echocardiographic measurements were taken in conscious and anesthetized pigeons in the right parasternal longitudinal horizontal heart view.

RESULTS

The results demonstrated a significant decrease in heart rate, systolic and diastolic A' wave myocardial velocities. The diastolic E' wave velocities were less influenced by anesthesia and significantly decreased only for some heart wall segments. The systolic myocardial velocities were significantly negatively correlated with the heart rate. Using the TDI curve, the isovolumic contraction (IVC) and relaxation time (IVR) and the time of atrioventricular delay during anesthesia could be determined. There is a significant increase in IVR and atrioventricular delay during anesthesia CONCLUSION AND CLINICAL RELEVANCEN: A higher heart rate in anesthesia should be interpreted as a compensation for reduced heart performance. The results of the present study indicate the necessity for establishing normal heart values in conscious and anesthetized pigeons.

Diastolic and Systolic Longitudinal Myocardial Velocities of Healthy Racing Pigeons (Columba livia f. domestica) Measured by Tissue Doppler Imaging

Tissue Doppler imaging (TDI) is a noninvasive sonographic method of acquiring and quantifying myocardial velocities. This technique is used in human and small animal medicine to diagnose cardiac diseases. Using this technique, we evaluated the longitudinal myocardial peak velocities of the interventricular septum, and the left and right ventricular free walls in the systole and diastole in 40 racing pigeons. The TDI examinations confirmed the movement of the heart base toward the apex in the systole and away from the apex in the diastole. Inhomogeneous distribution of the myocardial velocities with a statistically significant velocity gradient from the basal to the apical myocardial segments was found. The left and right free walls have significantly higher myocardial velocities than the myocardium of the septum. The myocardial velocities during active ventricular filling were significantly higher in the right ventricular free wall than in the left one. The validation of the method resulted in coefficients of variation between 3% and 33% for the systolic and 3% and 75% for the diastolic individual myocardial velocities. Weekly repeated measurements resulted in variation coefficients between 3% and 45% for systolic and diastolic myocardial velocities, respectively.

Color Flow Doppler Echocardiography in Healthy Racing Pigeons (Columba livia f. domestica) and the Evidence of Physiological Blood Flow Vortex Formations

In avian medicine, Doppler sonographic techniques are used to visualize and estimate blood flow in the heart. In the literature there is a lack of standardized studies of the use of color Doppler flow on healthy avian species. For this purpose, we examined blood flow in the heart in the four-chamber view of clinically healthy awake racing pigeons (n = 43) by color flow Doppler sonography. With this technique the diastolic and systolic blood flow in the heart chambers and the heart valve regions were well visualized. However, the pulse repetition frequency must be adapted to the specific blood flow velocities of the heart region to be measured to reduce aliasing in higher velocities and to visualize blood flow of lower velocities. With the help of color Doppler imaging in the four-chamber view, typical physiological atrial and ventricular blood flow vortex formations were visualized in the avian heart for the first time. In the left ventricle an asymmetric vortex ring in the passive and active ventricular filling, in the right ventricle a great counter-clockwise blood vortex in the active ventricular filling, in the left atrium a vortex clockwise, and in the right atrium counter-clockwise were observed. The knowledge of these physiological blood flow vortices is important to identify pathological blood flow.