Long-Term Effects of High-Intensity Interval Training (HIIT) on Cardiac Function and Mortality in Heart Failure

INTRODUCTION: Heart failure (HF) is one of the causes of morbidity and mortality. High-intensity interval training (HIIT) has been suggested as a positive intervention that can be practiced to help optimize heart function and overall health. However, the effect of HIIT in the long-term on heart functioning, the level of symptoms shown by patients with HF, and the survival of the affected people are poorly understood. This study explores the effects of a long-term HIIT intervention on individuals who have HF. METHODS: This was a longitudinal observational study conducted in the cardiac department of Pakistan Institute of Medical Sciences (PIMS) in Islamabad, Pakistan, from July 2024 to January 2025. Purposive non-probability sampling was used to recruit all HF patients, with 158 patients aged 30 years and older participating. The demographic information and research instruments used at baseline, three months, and six months include the Kansas City Cardiomyopathy Questionnaire (KCCQ-12), Duke Activity Status Index (DASI) questionnaires, and New York Heart Association (NYHA) classification. IBM SPSS version 26 (IBM Corp., Armonk, NY, US) was used to conduct statistical tests, including repeated-measures ANOVA, Pearson correlation, and multiple linear regression. RESULTS: The sample size consisted of 158 participants (N = 113, 71.0% men; N = 45, 29.0% women), with a mean age of 56.3 ± 12.4 years. There was a significant improvement in both KCCQ-12 and DASI (p < 0.01), whereas the NYHA classification worsened (p < 0.001). Increased levels of HIIT were associated with improved functional capacity and quality of life (r = 0.392, p < 0.01 for DASI; r = 0.215, p < 0.01 for KCCQ-12) and reduced symptom severity (r = -0.265, p < 0.01 for NYHA). The main predictors of these outcomes identified through regression analysis included HIIT, age, gender, and comorbidities. Gender differences were demonstrated by women reporting better outcomes and men exhibiting worse indicators concerning symptoms. CONCLUSION: Long-term HIIT is highly effective in improving cardiac performance, decreasing the severity of HF symptoms, and improving the quality of life among HF patients. These findings demonstrate the promising potential of HIIT as an effective adjunctive treatment in managing HF, as it can bring significant benefits to patients of diverse ages and backgrounds. Early HIIT, tailored to the individual needs of each patient, has the potential to improve clinical outcomes and increase survival rates in HF populations.