Adaptation of the left ventricle to sudden changes in heart rate in patients with artificial pacemakers

Karlöf, I.; Bevegård, Sture; Ovenfors, Carl-Olof

doi:10.1093/cvr/7.3.322

Cited by 21 publications

(3 citation statements)

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“…This may be due, in part, to the fact that stroke volume contributes relatively less than increased heart rate in driving the cardiac output to meet the demands of exercise, as suggested by several studies comparing rate responsive single chamber pacemakers with AV pacing. 43,[55][56][57] Overall, during exercise, stroke volume increases by only 50% compared to a 200%-300% increase in heart rate. 5 While the authors' first hypothesis was refuted by the findings that optimizing the AV interval did not improve exercise tolerance, the results demonstrate that rate adaptive AV interval is useful in enhancing exercise performance.…”

Section: Discussionmentioning

confidence: 99%

Atrioventricular Interval Optimization and Exercise Tolerance

Khairy

Talajic

Domínguez

et al. 2001

Pacing Clinical Electrophis

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Modern pacemakers offer many programming options regarding the AV interval including the ability to vary AV intervals depending on whether atrial activity is paced or spontaneous and to shorten AV intervals with increasing rates. To determine if optimization of these features improves exercise tolerance, 14 patients with intact sinus node function and AV block treated with dual chamber pacemakers were enrolled in a randomized double-blind crossover trial. Doppler echocardiographic measurements of cardiac index and mitral flow were assessed over a range of programmable AV intervals at rest to determine each patient's optimal AV interval. Eleven patients completed serial graded exercise tests with spiroergometry after randomly programming the AV interval three ways in a crossover manner: fixed AV interval = 150 ms without rate adaptation (150/Fixed), fixed AVinterval = 150 ms with rate adaptation (150/R), or optimized AV interval with rate adaptive AV interval shortening (optimized/R). Exercise capacity was determined by maximum oxygen uptake. Ten men and four women, age 64 +/- 8 years, were enrolled. At rest, optimization of the AVintervalimproved the cardiac index by 21% (P < 0.001) and mitral flow by 13.4% (P < 0.001) when compared to least-favorable AV intervals. During exercise, no differences in maximum heart rates were noted. Maximum oxygen uptake was increased in both groups with rate adaptive AVinterval shortening when compared tofixed AVinterval without rate adaptation: 13.9% (adjusted P < 0.04) and 14.6% (adjusted P < 0.02) in optimized/R and 150/R, respectively. No differences were noted between optimized/R and 150/R. In conclusion, rate adaptive AV interval shortening improved exercise tolerance independent of changes in heart rate. However, optimization of the AV interval with Doppler echocardiography at rest did not further improve exercise capacity.

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Section: Discussionmentioning

confidence: 99%

Atrioventricular Interval Optimization and Exercise Tolerance

Khairy

Talajic

Domínguez

et al. 2001

Pacing Clinical Electrophis

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“…Valins, 1966) ; and (b) if behavioral effects are observed to result from an exogenous change in heart rate, then causal direction of the observed association is established. this setting contained no resources for the measurement of any physiological process besides heart rate, but previous research has demonstrated that paced changes in heart rate (within the range of rates employed in the present research-i.e., 72-88 beats per minute) are unaccompanied by significant changes in normal visceral, somatic, or cardiac-output responses (e.g., Gill, Jakobi, Morton, & Wechsler, 197S;Karlof, Bevegard, & Ovenfors, 1973).…”

Section: Methodological Considerationsmentioning

confidence: 99%

Effects of exogenous changes in heart rate on facilitation of thought and resistance to persuasion.

Cacioppo¹

1979

Journal of Personality and Social Psychology

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Two experiments were conducted to examine the effects of an accelerated heart rate on information processing and resistance to persuasion. Experiment 1 addressed the effects on cognitive performance of manipulating heart rate exogenously for brief periods of time. Fourteen subjects wearing implanted demand-type cardiac pacemakers performed reading comprehension and sentence generation tasks while their heart rate was either accelerated or not accelerated. Results revealed that performance was better when heart rate was accelerated than when it was not accelerated. Experiment 2 addressed the effects on counterargumentation and resistance to persuasion of manipulating heart rate using the cardiac-pacing technique employed in Experiment 1. Subjects read highly involving counterattitudinal communications while their heart rate was either ostensibly or actually accelerated. Accelerated heart rate resulted in the generation of more total thoughts and counterarguments than did basal heart rate; resistance to persuasion was related significantly to the number of counterarguments generated. The methodology used provides a means by which social psychologists can study the effects on social processes of actual but unperceived changes in physiological processes.

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“…The increased cardiac output is associated with reductions in sympathetic tone, atrial rate and end-diastolic ventricular volume, and occurs despite a reduction in stroke volume and ventricular contractility. 25 41 46 Early studies suggested that the maximal increase in cardiac output during ventricular pacing at rest occurs between 70 and 90 beats min ±1 . Any further increase or decrease in pacing rate diminishes cardiac output and increases peripheral vascular resistance.…”

Section: The Importance Of Atrioventricular Timingmentioning

confidence: 99%