Hemodynamics and the influence of anesthetics on the electrical properties of the rainbow trout heart

We used noninvasive ultrasound and electrocardiography to further understand electrical and mechanical dynamics of the working trout heart in vivo. We have established new electromechanical reference data, characterized the influence of commonly used anesthetics on the electrical properties of the trout heart, and developed an inquiry-based, experiment-friendly, cardiac physiology laboratory for use in undergraduate physiology courses.; Using Doppler echocardiography and electrocardiography, we show that trout preserve normal cardiac function during maturation-associated cardiac enlargement; a finding consistent with earlier work suggesting biochemical compensation during cardiac hypertrophy. This contrasts with mammalian pattern of hypertrophy, which often results in decompensation and pathology. We propose that the long QT interval, and the cessation of ventricular ejection prior to the T-wave in trout, permit cardiac output adjustment through stroke volume modification, the predominate pattern in teleost fishes. We promote the use of echocardiography in studies of fish cardiovascular physiology and morphometrics.; The widespread use of fish anesthetics for commercial and research purposes merits a better understanding of their effects on cardiac electrical properties. Comparable doses of tricaine, benzocaine, and clove oil exhibit differential effects on electrical activity of the trout heart. Heart rate variability and QRS duration were significantly higher under benzocaine anesthesia, a result suggesting benzocaine-induced hypoxia or toxicity. These effects may influence cardiac function studies using benzocaine. The similar effects of tricaine and clove oil suggest similar autonomic mechanisms, and support the use of clove oil as an inexpensive, easy-to-use fish anesthetic.; As an extension of our research, we have developed a noninvasive, undergraduate laboratory of cardiac physiology that can be easily incorporated into a comparative physiology curriculum. The student-friendly protocol promotes understanding of the vertebrate electrocardiogram using an inquiry-based approach. Aside from gaining knowledge of cardiac function, the student gains valuable experience in scientific inquiry, study design, developing scientific protocols, and animal care.