Heart rate turbulence assessed through ergometry after myocardial infarction: a feasibility study

ABSTRACT BACKGROUND: Coronary artery disease is an important cause of morbidity and mortality. The impact of ventricular arrhythmias with impaired cardiac vagal activity is one of the most recently studied prognostic factors. However, there are no studies evaluating the phenomenon of heart rate turbulence (HRT) during physical exertion. OBJECTIVE: To study the behavior of HRT during exercise testing, among individuals after myocardial infarction. DESIGN AND SETTING: Feasibility study conducted in a university hospital among individuals 4-6 weeks after myocardial infarction. METHODS: All subjects underwent 24-hour Holter monitoring and ergometric stress testing. We considered that abnormal HRT was present if the turbulence onset was ≥ 0% or turbulence slope was ≤ 2.5 mm/relative risk interval. RESULTS: All 32 subjects were asymptomatic. Their median age was 58 years (interquartile range 12.8) and 70% were male. Abnormal HRT was associated with ventricular dysfunction in this population. We found no differences regarding the behavior of HRT, in relation to age, gender, smoking, systemic arterial hypertension, diabetes mellitus or dyslipidemia. Ergometric stress testing detected premature ventricular beats (PVB) in approximately 44% of the examinations, and these occurred both during the active phase of effort and in the recovery period. The low occurrence of several isolated PVB in beta-blocked subjects made it difficult to perform statistical analysis to correlate HRT between ergometric and Holter testing. CONCLUSION: The data obtained in this study do not support performing HRT through ergometric stress testing among patients who remain on beta-blockers post-myocardial infarction, for the purpose of assessing cardiac vagal activity.

研究背景：冠状动脉疾病是引发疾病发病率与死亡率的重要病因。伴心脏迷走神经功能受损的室性心律失常是近年备受关注的预后影响因素之一，但目前尚无针对体力负荷过程中心率震荡（heart rate turbulence, HRT）现象的评估研究。
研究目的：探究心肌梗死后受试者在运动负荷试验（ergometric stress testing）过程中的心率震荡变化特征。
研究设计与研究场所：本可行性研究于大学附属医院开展，研究对象为心肌梗死后4~6周的个体。
研究方法：所有受试者均接受24小时动态心电图（24-hour Holter monitoring）监测与运动负荷试验。本研究定义，当震荡起始≥0%或震荡斜率≤2.5 mm/相对RR间期时，判定为心率震荡异常。
研究结果：全部32名受试者均无临床症状，中位年龄为58岁（四分位间距12.8），其中70%为男性。该人群中，心率震荡异常与心室功能不全存在关联。未观察到心率震荡变化特征与年龄、性别、吸烟史、系统性动脉高血压、糖尿病或血脂异常存在相关性。运动负荷试验在约44%的检测中检出室性早搏（premature ventricular beats, PVB），此类早搏既可发生于运动负荷阶段，也可出现在恢复期。由于接受β受体阻滞剂治疗的受试者中孤立性室性早搏发生频次较低，难以开展统计学分析以对比运动负荷试验与Holter监测中的心率震荡指标。
研究结论：本研究所得数据不支持在心肌梗死后仍接受β受体阻滞剂治疗的患者中，通过运动负荷试验检测心率震荡来评估心脏迷走神经功能。