Table 1. A literature review of various studies providing evidence regarding the efficacy of HIIT in clinical outcomes of cardiovascular disease patients.

ACS: acute coronary syndrome; AIT: aerobic intensity training; BDI: Beck depression inventory; BDNF: brain-derived neurotrophic factor; BP: blood pressure; CABG: coronary artery bypass grafting; CAD: coronary artery disease; CHF: chronic heart failure; HIIT: high-intensity interval training; HRQoL: health-related quality of life; HR: heart rate; IHD: ischemic heart disease; LVEF: left ventricle ejection fraction; MCT: moderate continuous training; MI: myocardial infarction; MICT: moderate-intensity continuous training; MISS: moderate intensity steady state; RCT: randomized control trial; SF-36: short form 36; VO2: oxygen consumption

Author	Study Type	Study Population	Sample Size	HIIT Protocol	Control	Outcomes	Results	Conclusion
Wisløff et al. [15] 2007 Norway	RCT trial	Postinfarction heart failure patients	27 (mean age 75.5 ± 11.1 years)	HIIT: 95% max HR, 3x per week, for 12 weeks	MCT: 70% of max heart rate, 3x per week for total 12 weeks	VO₂ peak, LVEF, cardiac remodeling, endothelial function, quality of life	VO₂ peak increased more with HIIT (46%) than with MCT (14%, p < 0.001). Only the HIIT group significantly improved LVEF, and LV volume levels. Both groups improved quality of life scores.	Higher-intensity training is essential for reversing LV remodeling and improving overall cardiovascular health in post-infarction heart failure patients.
Moholdt et al. [16] 2009 Norway	RCT trial	Post CABG patients	59	AIT: 90% max HR, 5x per week, for 4 weeks	MCT: 70% max heart rate, 5x per week for 4 weeks	Vo₂ peak, quality of life	Both groups increased VO2 peak from baseline to 4 weeks, with the AIT group improving further by 6 months. Quality of life also improved in both groups.	Both AIT and MCT provide short-term benefits after CABG, but AIT leads to superior long-term improvements in VO₂ peak.
Conraads et al. [17] 2015 Belgium	Multicenter, prospective, RCT trial	CAD patients	200 (mean age 58.4 ± 9.1 years)	AIT: 95% peak HR, 3x per week, for a total 12 weeks	MCT: 70% peak HR, 3x per week, for total 12 weeks	Cardiovascular risk factors, safety, VO₂ peak, endothelial function, HRQoL	Peak VO₂ augmented in AIT (22.7%) and MCT (20.3%; p < 0.001). Flow-mediated dilation improved more in AIT (+34.1%) than in MCT (+7.14%; p < 0.001). Equal improvement of cardiovascular risk factors & quality of life.	AIT and MCT produced comparable improvements in peripheral endothelial function and exercise capacity in CAD patients, contradicting earlier trials with different outcomes.
Jaureguizar et al. [18] 2016 Spain	Randomized clinical trial	IHD patients	72	HIIT: 3x per week, for 8 weeks	MCT: for 8 weeks	Vo₂ peak, aerobic threshold, quality of life, 6-minute walk distance test, HRQoL	HIIT amplified VO₂ peak by 4.5 ± 4.7 vs. MCT's 2.5 ± 3.6 mL·kg·min (p < 0.05) and 6-minute walk by 49.6 ± 6.3 m, MCT by 29.6 ± 12.0 m (p < 0.05). HRQoL improved in both groups.	HIIT enhances quality of life and functional capacity in cardiac rehabilitation without increasing cardiovascular risk.
Nytrøen et al. [19] 2019 Norway	Multicenter, prospective, RCT trial	Heart transplant patients	81 (73% men)	HIIT: 85%–95% of peak effort, at 4×4-minute intervals, for 9 months	MICT: 60%–80% of peak effort for 9 months	VO₂ peak, anaerobic threshold, health-related quality of life, muscular strength, body composition	The HIIT group showed greater improvements in VO₂ peak, anaerobic threshold, and muscle capacity compared to the MCT group. HRQoL was similar, with no serious adverse events reported.	HIIT is safe and effective for improving exercise capacity in heart transplant recipients (de novo patients) compared to the MICT group.
Villafaina et al. [20] 2020 Spain	RCT trial	ACS patients	21 (HIIT and MICT groups)	HIIT: 90% HR with 15 seconds recovery, 10 sets of 15 seconds each, 2x per week, total 12 weeks	MICT for 40 minutes at 70%-75% HR, performed 2x per week for 12 weeks	Physical fitness, Body composition, HR variability, HRQoL	Both HIIT and MICT improved agility and mental HRQoL. HIIT showed greater gains in flexibility and handgrip strength (p < 0.05), with no substantial effects on cardiorespiratory fitness or HR variability.	HIIT is an effective and safe rehabilitation alternate for ACS patients, offering flexibility and strength benefits compared to MICT.
Papathanasiou et al. [21] 2020 Bulgaria	Single-blind, prospective RCT trial	CHF patients	120 (mean age 63.73 ± 6.68 years)	m-Ullevaal protocol: 3 sittings per week for a total of 12 weeks	MICT: 3 sittings per week for a total 12 weeks	6-minute walk test VO₂ peak, LVEF, perceived exertion scale, HRQoL	Both interventions significantly improved functional exercise capacity, LVEF, perceived exertion, and HRQoL (p < 0.001), with the m-Ullevaal protocol showing greater gains than MICT (p < 0.001).	The m-Ullevaal protocol is more effective than MICT for improving the quality of life and exercise capacity in CHF patients, and physicians can effectively implement it in cardiac rehabilitation.
Taylor et al. [22] 2020 Australia	Randomized clinical trial	Angiographically proven CAD patients	96	HIIT: 85%–95% of peak effort, at 4×4-minute intervals for 4 weeks, then home-based for 48 weeks	40-min MICT, 3 sessions/week for 4 weeks, then home-based for 48 weeks	VO₂ peak, feasibility, cardiovascular risk factors, safety, adherence, HRQoL	HIIT improved VO₂ peak by 10% after 4 weeks compared to 4% for MICT (P = .02). At 12 months, improvements were similar: HIIT at 10% and MICT at 7% (P = 0.30). Both groups demonstrated good feasibility and a little withdrawal rates.	HIIT is safe and effective, showing greater short-term VO₂ peak improvements than MICT, with similar long-term effects and adherence rates.
Yakut et al. [23] 2021 Turkey	RCT trial	MI patients	21	HIIT: 85–95% of HR reserve, 2x per week, total 12 weeks	MICT: 70–75% HR reserve, 2x per week, total 12 weeks	6-minute walk test, HR, BP, pulmonary function, respiratory muscle strength, HRQoL	Both HIIT and MICT improved resting blood pressure, HR, and functional capacity, However, HIIT was better than MICT in enhancing lower limb muscle strength and pulmonary functions (p < 0.05)	Both HIIT as well as MICT can be effectively useful at home for post-MI patients, significantly improving functional capacity and health outcomes.
Reed et al. [24] 2022 Canada	RCT trial	Post-revascularization CAD patients	135	HIIT: 4 × 4 min at 85%-95% peak HR, 2x per week, total 12 weeks	MICT: resting HR + 20-40 bpm, twice weekly for total 12 weeks	6 min walk test, depression (BDI-II), BDNF, quality of life (SF-36, HRQoL)	BDI-II scores improved across all groups, while BDNF levels remained unchanged. Significant enhancements were noted in SF-36 and HRQoL	All exercise programs were safe and well attended, with HIIT showing superior improvements in functional capacity, predicting future cardiovascular events.
McGregor et al. [25] 2023 UK	RCT trial	CAD patients	382 (HIIT: 187, MISS: 195)	HIIT: 10 × 1 min intervals at >85% peak HR, 2x per week, for eight weeks	MISS: 20-40 min at 60-80% peak HR, 2x per week, for eight weeks	VO₂ peak, cardiac structure and function, adverse events, HRQoL	VO₂ peak enhanced more with HIIT (2.37 mL/kg/min) than with MICT (1.32 mL/kg/min; P = 0.002). Only a single HIIT-related major adverse event was reported.	HIIT in low volume is safe and more effective than MISS for enhancing cardiorespiratory fitness in CAD patients, making it a valuable option for cardiac rehabilitation programs.