ISSN:
0003-276X
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Medicine
Notes:
While studying the electrocardiograms of developing hearts it was noted that an adult type ECG could not be obtained in an embryonic heart which could not be blocked with digitalis. The need to know more about heart-block was obvious. Intact embryos of 36 to 120 hours were floated on to glass plates and treated with digoxin-Tyrode solution. Before 36 ± hours no dissociation of beat could be produced. The heart just stopped. At 40 ± hours a conal block followed by a midventricular block appeared. At 42 ± hours conal and midventricular blocks were followed by the first appearance of AV block. It was intermittent. At 47 ± hours conal block jumped to an incisive AV block. Midventricular block was rare. At 72 hours conal and then AV block occurred. Combinations such as four atrial to two ventricular to one conal beat could be readily produced while blood circulated.Electrocardiograms and cinephotomicrographs were taken of 72 and 96 hour hearts. Most striking was the fact that the typical Wenckebach phenomenon of adult heart-block could be duplicated, i.e., an increase of PR interval preceding AV block followed by a shorter PR interval which again gradually increased preceding AV block. This sequence was repeated over and over. An explanation of these events is offered.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/ar.1091490205
