Beneficial effect of chronic bradycardial pacing on capillary growth and heart performance in volume overload heart hypertrophy.
We have previously reported that chronic bradycardial pacing increases both capillary density/mm2 (CD) and maximal work output in normal rabbit hearts. This technique has now been applied to rabbits with volume-overload hypertrophy due to lesion of the aortic valve. Four groups of animals were studied: controls (C), paced (P), valve-lesioned (VL), and paced valve-lesioned (PVL). The aortic valve was lesioned 8 weeks before the acute experiments; pacing was started 4 weeks before the acute experiments, and thus, the PVL group had developed hypertrophy before pacing was started. The degree of hypertrophy was similar in VL hearts whether paced or not: heart wt/body wt ratio increased by 33.5 +/- 8.9% (mean +/- SEM) in VL and 25.2 +/- 8.2% in PVL versus control animals of similar body weight (p less than 0.001). The hearts of the PVL animals showed a higher CD (2,277 +/- 107) than VL hearts (1,383 +/- 43), CD in C hearts of similar weights being 1,595 +/- 103, and in P hearts 2,350 +/- 194. Thus, CD was lower by 14% in VL and higher by 43% in PVL than in C hearts. Valve-lesioning had a significant effect in reducing maximal cardiac minute work (p less than 0.001), whereas pacing significantly improved maximal cardiac minute work (p less than 0.001) to 2.467 +/- 0.206 J/g x 10(-4) in the P group versus 1.609 +/- 0.105 in the C group.(ABSTRACT TRUNCATED AT 250 WORDS)
Wright
A J
AJ
Physiology Department, University of Birmingham Medical School, England.
Hudlicka
O
O
Brown
M D
MD
D000704:Analysis of Variance; D000818:Animals; D001022:Aortic Valve Insufficiency / Q000503:physiopathology; D001794:Blood Pressure; D002196:Capillaries / Q000254:growth & development*; D002302:Cardiac Output; D002304:Cardiac Pacing, Artificial; D006332:Cardiomegaly / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy; D005260:Female; D006321:Heart / Q000033:anatomy & histology / Q000503:physiopathology*; D006339:Heart Rate; D008297:Male; D009929:Organ Size; D011817:Rabbits