Researching impaired heart rate recovery index in patients who have had COVID-19

Heart rate recovery index (HRRI) occurs as a result of vagal reactivation and sympathetic retraction and is an independent risk factor used to assess autonomic nervous system (ANS) function and to determine prognosis in cardiovascular disease and all-cause mortality. It has been shown in various studies that cardiac autonomic dysfunction due to COVID-19 can occur. The aim of our study is to evaluate the effect of COVID-19 on ANS functions in people who have had this disease with HRRI.

In this prospective and observational study, patients proven to have had COVID by molecular methods (polymerase chain reaction positivity) and healthy controls were examined. Electrocardiogram, Transthoracic Echocardiography, Hemogram and Biochemistry tests, and exercise stress test were performed in both groups. HRRIs were calculated by subtracting heart rates at the 1^st, 2^nd, 3^rd, 4^th, and 5^th min during the post-exercise relaxation phase from the peak heart rate during exercise. P<0.05 were considered significant.

Study group (n=30) (Female/Male; n=15/15; mean age=39.8±13.3 years; median body mass index=25.9 kg/m²) and control group's (n=33) (Female)/Male; n=16/17; mean age=41.9±13.2 years; median body mass index=27.2 kg/m²). 1^st min and 2^nd min relaxation heart rates in the COVID-19 (+) group were found to be significantly higher than in the control group (p=0.042, p=0.049, respectively). In the COVID-19 (+) group, the 1^st min, 2^nd min, and 3^rd min HRRI were found to be significantly lower than in the control group (p<0.001, p=0.006, p=0.039, respectively).

According to the results of our study, HRRI is impaired as an indicator of autonomic dysfunction in people who have had COVID-19. This situation correlates with other studies that have results of ANS dysfunction due to COVID-19, and this may pose a risk factor for increased mortality and morbidity.