Micro-electrocardiograms to study post-ventricular amputation of zebrafish heart.
The zebrafish (Danio rerio) is an emerging model for cardiovascular research. The zebrafish heart regenerates after 20% ventricular amputation. However, assessment of the physiological responses during heart regeneration has been hampered by the small size of the heart and the necessity of conducting experiments in an aqueous environment. We developed a methodology to monitor a real-time surface electrocardiogram (ECG) by the use of micro-electrodes, signal amplification, and a low pass-filter at a sampling rate of 1 kHz. Wavelet transform was used to further remove ambient noises. Rather than paralyzing the fish, we performed mild sedation by placing the fish in a water bath mixed with MS-222 (tricane methanesulfonate). We recorded distinct P waves for atrial contraction, QRS complexes for ventricular depolarization, and QT intervals for ventricular repolarization prior to, and 2 and 4 days post-amputation (dpa). Sedation reduced the mean fish heart rate from 149 +/- 18 to 90 +/- 17 beats/min. The PR and QRS intervals remained unchanged in response to ventricular apical amputation (n = 6, p > 0.05). Corrected QT intervals (QTc) were shortened 4 dpa (n = 6, p < 0.05). In a parallel study, histology revealed that apical thrombi were replaced with fibrin clots and collagen fibers. Atrial arrhythmia was noted in response to prolonged sedation. Unlike the human counterpart, ventricular tachycardia or fibrillation was not observed in response to ventricular amputation 2 and 4 dpa. Taken together, we demonstrated a minimally invasive methodology to monitor zebrafish heart function, electrical activities, and regeneration in real-time.
Sun
Ping
P
Department of Biomedical Engineering and Division of Cardiovascular Medicine, University of Southern California, Los Angeles, CA, USA.
Zhang
Yolanda
Y
Yu
Fei
F
Parks
Elizabeth
E
Lyman
Althea
A
Wu
Qiong
Q
Ai
Lisong
L
Hu
Chang-Hong
CH
Zhou
Qifa
Q
Shung
Kirk
K
Lien
Ching-Ling
CL
Hsiai
Tzung K
TK
D000671:Amputation, Surgical; D000818:Animals; D016477:Artifacts; D004562:Electrocardiography; D006321:Heart / Q000502:physiology*; D006352:Heart Ventricles / Q000601:surgery; D023421:Models, Animal; D009206:Myocardium / Q000473:pathology; D012038:Regeneration / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D015027:Zebrafish