EVALUATION OF SYSTOLIC TIME INTERVALS AND HEART RATE VARIABILITY AS INDICATORS OF CARDIAC AUTONOMIC FUNCTION AMONG MALE ISCHEMIC HEART DISEASE PATIENTS

Abstract

Background and Objectives: Evaluation of Left ventricular (LV) systolic function is based on ejection fraction assessment. Due to the ease of measurement, systolic time intervals (STI) are ideally suitable for studying LV performance. Heart rate variability (HRV) is the variation in heart rate from beat-to-beat and is a crucial non-invasive method for examining the function of the autonomic nerve system of the heart. Ischemic heart disease (IHD) patients are frequently thought to be in a sympathetically predominant state. Percutaneous coronary intervention (PCI) for the treatment of myocardial ischemia may help to regain autonomic balance. Hence, this study aimed to evaluate STI and HRV measures, after successful revascularisation by PCI among IHD patients. Materials and Methods: A total of 229 consecutive male IHD patients with acute coronary syndrome planned for coronary angiography were recruited. Among them, 197 patients (aged 54.09 ± 11.75 years) were included in this study. Out of the included 145 patients underwent PCI. In accordance, to calculate the systolic time intervals [pre-ejection period (PEP), and LV ejection time (LVET), and total electro-mechanical systole (QS2)] 2D and pulsed-Doppler echocardiography was performed. In addition, fifteen minutes of ECG recording was done to measure short-term HRV indices and time- [root mean square deviation of N-N intervals (SDNN), root-mean-square of consecutive N-N intervals variations' (rMSSD)] and frequency-domain [low-frequency (LF) power, high-frequency (HF) power and total power (TP)] HRV indices were evaluated. Pre- and post-PCI measurements were taken for each measurement. Further, the Short Form-12 health survey questionnaire has been used to examine patients' quality of life (QoL) post-PCI. xix Results: On admission, PEP and PEP/LVET ratios were higher when compared to 24h post- PCI. LVET increased in 24h post-PCI and sustained at 6 months when compared to the values obtained on admission. Besides, QS2 increased at 24h post-PCI and decreased at 3- month which did not reach baseline even after 6 months of follow-up. In addition, admission SDNN, rMSSD, TP, LF, HF, and HFnu values were higher when compared to 24h post-PCI with the LFnu and LF/HF being lesser. Further, when compared to 24h post-PCI HRV values, there was an increase in SDNN, rMSSD, LF, HF, and HFnu with a decrease in LFnu and LF/HF at 3- and 6-month post-PCI which did not reach baseline even after 6-months following revascularisation. Further, major adverse cardiac events (death and re-acute MI) occurred in 12 (6.1%) out of 197 IHD patients, during a follow-up of six months. When compared to the SF-12 mental component score, which over time appears to improve without achieving statistical significance, physical component score was found to have significantly improved. We discovered a substantial positive connection between left ventricular ejection fraction and QoL among ACS patients who had not experienced a MACE. Also, on correlation analysis, measures of STI correlated well with HRV. Further on regression analysis, these modifications in neurocardiac regulation measurements were connected with risk variables and medicines. Conclusion: Present study could efficiently evaluate STI and HRV. Findings suggest that patients with IHD who underwent PCI infer altered cardiac autonomic balance with this surgical procedure. Yet there was a gradual reversal of sympathetic dominance and restoration of parasympathetic tone on follow-up. The present study still has limitations regarding HRV's subsequent sensitivity and specificity. Particularly, it has a modest specificity (61% to 73%) and a higher sensitivity (43% to 86%). Hence, this method might have impending applications in the management of IHD. Additionally, these measures possibly are potentially used as prognostic tools in future studies.