Development of more erratic heart rate patterns is associated with mortality post–myocardial infarction

Abstract

Cardiac patients often have sinus arrhythmia of non-respiratory origin [erratic sinus rhythm" (ESR)]. ESR was quantified using hourly Poincaré and power spectral HRV plots from normal-to-normal interbeat intervals (N-Ns) and hourly values of the short-term fractal scaling exponent and correlations of N-Ns in N=60 non-survivors and N=66 randomly-selected survivors in the Cardiac Arrhythmia Suppression Trial. Hours were coded (ABN) as normal (0), borderline (0.5) or ESR (1). T-tests compared ABN for N=2413 paired hours at baseline and on therapy. ABN was higher in nonsurvivors (0.38 ± 0.44 vs. 0.28 ± 0.40, baseline and 0.51 ± 0.45 vs. 0.34 ± 0.43, on therapy, p<0.001). Increased ABN with treatment was greater in non-survivors. Normal hours at baseline (RR=0.77, 095% CI=0.62−0.96, p=0.018) and on treatment (RR=0.47, 95%CI=0.39−0.58) were significantly associated with decreased mortality compared to ESR. Quantification of ESR may identify more vulnerable patients or help monitor the effects of pharmacological treatment. Keywordsheart rate; risk factor; mortality; post-MI; anti-arrhythmic The analysis of heart rate variability (HRV) provides information about cardiac autonomic function. However, we have found that many older subjects and patients with cardiovascular disease have an increased beat-to-beat variability that is irregular and does not reflect underlying respiratory sinus arrhythmia (1). We have called this erratic rhythm. The presence of erratic rhythm, which is frequently episodic, increases values for short-term HRV indices such as rMSSD [root mean square of successive differences of normal-to-normal (N-N) interbeat intervals in ms], pNN50 [the % of N-N intervals >50 ms different from the previous interval) and high frequency power (the amount of variance in N-N intervals at respiratory frequencies, i.e., 0.15−0.4 Hz) that quantify beat-to-beat variability. Thus, in the presence of erratic rhythm, increased short-term HRV does not, as it does for younger people, necessarily reflect greater parasympathetic control of heart rate. A high prevalence of erratic rhythm may also explain why HRV measures that are believed to reflect parasympathetic function have relatively little predictive value for outcomes. At the same time, some "non-linear" HRV measures like the short-term fractal scaling exponent, (DFA1), and (SD12), the ratio of the axes of an ellipse fitted to the Poincaré plot do capture the presence of erratic rhythm (2,3).

Heart rate variability measured early in patients with evolving acute coronary syndrome and 1-year outcomes of rehospitalization and mortality

“…High NHF power in conjunction with low DFA1 in rehospitalized patients is consistent with the finding of erratic rhythm in relation to poorer outcomes, described by Stein et al17 The presence of an erratic rhythm may misleadingly elevate values of short-term HRV indices, such as HF power 17…”

“…Poincaré plots are graphic representations of coordinates corresponding to consecutive normal RR intervals, and were generated for each patient to visualize HRV organization and explore nonlinear HRV characteristics. The Poincaré ratio is the ratio of axes of an ellipse fitted to the plot (SD1= short axis/SD2= long axis, ratio = SD12), reflecting short-term, beat-to-beat variation compared to long-term, continuous variation 7,15–17…”

Autonomic nervous system dysfunction in psychiatric disorders and the impact of psychotropic medications: a systematic review and meta-analysis

“…24,25 Prospective evidence indicates that reductions in HRV are strongly associated with higher incidence of first cardiac events in patients without known cardiovascular disease 26 and predicts the later development of cardiovascular disease. 27,28 Reductions in HRV have therefore been considered a marker for various disease states, most notably a greater risk for cardiovascular disease and all-cause mortality. 29,30 …”

Breakdown of the Intermediate-Term Fractal Scaling Exponent in Sinus Node Dysfunction - New Method for Non-Invasive Evaluation of Sinus Node Function -

“…Heart rate behavior would be erratic if the sinus node, as a receptive end-organ of the neuroautonomic regulatory system, decoupled from the system. 24 Likewise, the increase of HF power, also a measure of vagal activity, in the patient with SND should be interpreted in the same way. Bergfeldt et al found elevated HRV in patients with advanced sick sinus syndrome, 3 and suggested that HRV could be used as a diagnostic or screening measure for SND.…”