Effect of heart rate on myocardial blood flow in dogs with left ventricular hypertrophy

1980 ◽  
Vol 239 (5) ◽  
pp. H621-H627
Author(s):  
T. R. Vrobel ◽  
W. S. Ring ◽  
R. W. Anderson ◽  
R. W. Emery ◽  
R. J. Bache
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Left Ventricular Hypertrophy ◽  
Myocardial Blood Flow ◽  
Ventricular Hypertrophy ◽  
Lateral Wall ◽  
Left Ventricular ◽  
Myocardial Mass ◽  
Previous Suggestion ◽  
Heart Rates

Because of the previous suggestion that subendocardial perfusion may be inadequate in the hypertrophied heart, this study was carried out to examine the response of transmural myocardial blood flow to pacing induced tachycardia in dogs with chronic left ventricular hypertrophy. Myocardial hypertrophy, produced by banding the ascending aorta of puppies at 5-6 wk of age, resulted in an 87% average increase in relative left ventricular mass compared with the control dogs. Myocardial blood flow was examined during ventricular pacing at heart rates of 100, 200, and 250 beats/min using radionuclide-labeled microspheres. Mean blood flow per unit myocardial mass was similar in the two groups of dogs at a heart rate of 100 beats/min and increased regularly during pacing in both groups of animals. Increasing heart rates did not change the transmural pattern of myocardial blood flow in the normal dogs, but in the animals with left ventricular hypertrophy pacing at 250 beats/min resulted in a significant redistribution of perfusion away from the subendocardium, with the ratio of subendocardial/subepicardial blood flow falling from 1.03 +/- 0.08 at 100 beats/min to 0.83 +/0 0.06 at 250 beats/min (P < 0.01). This redistribution of blood flow away from the subendocardium was especially marked in the regions encompassing the papillary muscles and the intervening left ventricular lateral wall.

Myocardial flow during tachycardia in dogs with chronic left ventricular hypertrophy

1986 ◽  
Vol 250 (6) ◽  
pp. H968-H973 ◽  
Author(s):  
J. C. Rembert ◽  
J. C. Greenfield
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Left Ventricular Hypertrophy ◽  
Myocardial Blood Flow ◽  
Aortic Coarctation ◽  
Ventricular Hypertrophy ◽  
Flow Distribution ◽  
Left Ventricular ◽  
Blood Flow Distribution ◽  
Myocardial Flow

The effect of pacing-induced tachycardia on transmural myocardial blood flow distribution was studied in 16 awake dogs with left ventricular hypertrophy secondary to modified aortic coarctation banding done at 7-10 wk of age. They were studied between 11 and 50 mo of age. In those dogs with mild and moderate left ventricular hypertrophy, the blood flow distribution was normal during resting conditions and remained normal during an increased heart rate of 250 beats/min. In the six dogs with severe hypertrophy (left ventricle/body wt greater than 7.0 g/kg) a reduced flow to the endocardial layers was present during resting conditions (endocardial/epicardial 0.91 +/- 0.09), but during tachycardia the endocardial-to-epicardial ratio normalized to 1.26 +/- 0.08 (mean +/- SEM). These data indicate that, in dogs with significant left ventricular hypertrophy, the vasoregulator mechanism functions adequately to maintain normal transmural myocardial blood flow distribution during tachycardia. In addition, studies were carried out to compare the magnitude of hypertrophy with the hemodynamic load secondary to coarctation banding.

scholarly journals Hemodynamic Consequence of Different Pacing Modes after Aortic Valve Replacement

2018 ◽  
Vol 21 (2) ◽  
pp. 090
Author(s):  
Arndt H Kiessling
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Aortic Valve ◽  
Left Ventricular Hypertrophy ◽  
Aortic Valve Replacement ◽  
Diastolic Function ◽  
Valve Replacement ◽  
Ventricular Hypertrophy ◽  
Left Ventricular ◽  
Heart Rates

Objectives: Ventricular pacemaker stimulation may cause deterioration of hemodynamics in patients with left-ventricular hypertrophy following aortic valve replacement. Since the diastolic function is often impaired, it remains unclear which heart rate best optimizes cardiac output. Low heart rates are suggested to treat impaired diastolic function chronically, but it is possible that cardiac output may be augmented by increasing the heart rate in patients with a fixed stroke volume (SV). The aim of this study is the identification of the best pacing mode and heart rate for the surrogate parameter SV and cardiac index(CI) in patients with left ventricular hypertrophy.Methods: Various pacemaker stimulation modes and different heart rates, as well as their influence on hemodynamics, were tested following aortic valve replacement in 48 patients with severe left-ventricular hypertrophy (Intraventricular septum (IVS)>1.5 cm) and aortic stenosis. SV and cardiac output were recorded by pulse curve analysis. Four modes of stimulation (right ventricular pacemaker stimulation (DDDright), left ventricular pacemaker stimulation (DDDleft), biventricular pacemaker stimulation (DDDbi), atrial pacemaker stimulation (AAI)) were documented at five different rates (60, 80, 100, 120, 140 beats/min) and three different postoperative time points (intraoperatively, 3h and 24h postoperatively).Results: The highest CI was found at linear rates between 60 to 140bpm. AAI was the best mode of stimulation in the majority of cases (35%), but in others, either left, right and/or biventricular stimulation was found to be better (15%). SV showed a u-shaped trend with a peak at 100 beats/min.Conclusion: An increase in the heart rate does not lead to a notable drop in SV postoperatively in left-ventricular hypertrophy; hence a rise in cardiac output can be anticipated up to a rate of 100 beats/min. A standardized response in terms of an ideal pacemaker stimulation mode could not be identified.

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