Sildenafil's effectiveness in the primary coronary slow flow phenomenon: a pilot randomised controlled clinical trial.

Background: On the one hand, the primary coronary slow flow phenomenon (CSFP) can cause recurrence of chest pain, prompting medical examinations and further healthcare costs, while on the other hand, it can lead to myocardial infarction, ventricular arrhythmia and sudden cardiac death. Nevertheless, there is not any agreement on the optimal treatment for primary CSFP, so we decided to examine the effectiveness of sildenafil in this context.

Methods: This pilot study is a 12-week, triple-blind, randomised, placebo-controlled trial for receiving either 50 mg daily oral sildenafil or placebo. Twenty eligible patients aged 30-70 years from a tertiary hospital in Yazd were randomly allocated in a 1:1 ratio to two groups. The primary outcomes were the alterations in functional capacity (metabolic equivalents, METs), Duke treadmill score (DTS) and angina severity (Canadian Cardiovascular Society (CCS) class). The study protocol registration code is IRCT20220223054103N1.

Results: The angina severity in the Sildenafil group improved, with all receivers achieving a state of being asymptomatic during regular physical activity (CCS I). Whereas just 40% of the recipients in the placebo group achieved the same level of improvement (p=0.011). Mean METs at baseline were 9.9 (SD: 3.1) and at week 12 were 13.1 (SD: 3.3) for sildenafil and 9.56 (SD: 2.1) and 9.63 (SD: 2.4) for placebo (difference favouring sildenafil with a median increase of 3.1 (IQR: 1.1 to 4.1, p=0.008)). Median DTS scores at baseline were 3 (IQR: 0 to 9) and at week 12 were 9.5 (IQR: 7.75 to 15) for sildenafil and 7 (IQR: -1.5 to 9.25) and 8 (IQR: 1.5 to 11.25) for placebo (difference favouring sildenafil with a median increase of 5.5 (IQR: 1 to 9.2, p=0.01)).

Conclusions: We suggest that a daily low dose of sildenafil could be a valuable therapeutic option for primary CSFP.

Trial Registration Number: IRCT20220223054103N1.