Rao Krishnamurti, Fisher Michael L, Robinson Shawn, Shorofsky Stephen, Gottlieb Stephen S
The University of Maryland School of Medicine and the Baltimore Veteran's Affairs Medical Center, Baltimore, Maryland, USA.
J Card Fail. 2007 May;13(4):269-74. doi: 10.1016/j.cardfail.2006.12.001.
Heart rate can affect cardiac function, but the importance of rates lower than 100 paced beats per minute is unknown. We therefore sought to evaluate the impact of different heart rates on ejection fraction, 6-minute walk, and peak oxygen consumption (VO2) in heart failure patients.
We studied 13 pacemaker-dependent New York Heart Association Class III patients with ejection fraction <40%, age 66 +/- 13. Eligible patients included those pacing at least 75% of the time at a lower set rate of 60 ppm. This was a 3-period randomized blinded crossover study. Patients were assigned to pace at 60, 75, or 90 ppm (with rate responsivity to 20 ppm above the lower rate) for 2 months at each setting. At the end of each period, ejection fraction (by nuclear ventriculography) and exercise tolerance (by peak VO2 and 6-minute walk) were assessed. Ejection fraction, peak VO2, and 6-minute walk distance were significantly different among the 3 heart rates. All 3 were depressed at 90 ppm. A heart rate of 90 also led to more clinical deterioration and premature discontinuation from that period.
Pacing at a heart rate of 90 led to lower ejection fraction, VO2, 6-minute walk distance and clinical evidence of worsening heart failure as compared with slower heart rates.
心率可影响心脏功能，但低于每分钟100次起搏心率的重要性尚不清楚。因此，我们试图评估不同心率对心力衰竭患者射血分数、6分钟步行距离和峰值耗氧量（VO₂）的影响。
我们研究了13例依赖起搏器的纽约心脏协会III级患者，射血分数<40%，年龄66±13岁。符合条件的患者包括那些至少75%的时间以60次/分钟的较低设定心率起搏的患者。这是一项为期3个阶段的随机双盲交叉研究。患者被分配在60、75或90次/分钟（心率反应性为比低心率高20次/分钟）的心率下各起搏2个月。在每个阶段结束时，评估射血分数（通过核心室造影）和运动耐量（通过峰值VO₂和6分钟步行试验）。3种心率下的射血分数、峰值VO₂和6分钟步行距离有显著差异。在90次/分钟时，所有3项指标均降低。心率为90次/分钟时还导致更多的临床恶化和该阶段的提前终止。
与较慢心率相比，心率为90次/分钟起搏导致射血分数、VO₂、6分钟步行距离降低以及心力衰竭恶化的临床证据。
