Echocardiographic evaluation of right ventricular function in patients with coronary slow flow

Introduction and Aim: Coronary Slow Flow Phenomenon (CSFP) is the clinical manifestation of slow passage of blood flow distally in coronary arteries without stenosis observed during coronary angiography. CSFP is seen in approximately 1% of coronary angiographies. Although the etiology and pathogenesis of CSFP have not been fully explained yet, it is currently believed that CSFP is associated with endothelial dysfunction, inflammatory response, microvascular reserve dysfunction, subclinical atherosclerosis, cell and platelet abnormalities, and genetic factors. Unstable angina is the most common clinical presentation, often including episodes of recurrent chest pain requiring readmission and reevaluation with associated electrocardiographic changes. Additionally, it can present with ST-segment elevation myocardial infarction (STEMI), non-ST-segment elevation myocardial infarction (NSTEMI), ventricular tachycardia (VT), and sudden cardiac death. Although limited, the literature includes studies evaluating left ventricular (LV) systolic and diastolic function using echocardiographic modalities, yielding different results. Data regarding the impact of CSFP on right ventricular (RV) myocardial function are limited and need further investigation. In our study, we aimed to evaluate RV functions using echocardiography in patients with CSFP and compare them with a control group matched for age and gender. Materials and Methods: The study included a total of 100 patients, with 50 patients exhibiting coronary slow flow on angiography due to suspected coronary artery disease, and 50 patients in the control group with normal coronary arteries. Echocardiographic measurements were obtained for all patients, including early diastolic filling velocity (triE wave), late diastolic filling velocity related to atrial contraction (triA wave), triE/A ratio, and tricuspid E deceleration time (triDT) at the level of tricuspid leaflet tips to annulus. Tricuspid annular plane systolic excursion (TAPSE) measurements were recorded. Measurements were also taken for right atrial pressure, tricuspid regurgitation (TR) jet velocity, and pulmonary artery pressure (PAP). Right ventricular fractional area change (RV FAC) was calculated. Early (triE') and late (triA') diastolic velocities, isovolumetric relaxation time (triIVRT), isovolumetric contraction time (triIVCT), triE'/A' ratio, triE/E' ratio, and a new parameter called TE-E' interval (time interval between tricuspid E and E') were measured using tissue Doppler imaging in the lateral tricuspid annulus. Results: There were no statistically significant differences between the two groups in terms of age, diabetes mellitus (DM), hyperlipidemia (HL), body mass index (BMI), gender, or smoking status. Coronary slow flow group had lower and statistically significant values for systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (p=0.024, p=0.031, and p=0.016, respectively). Patients with hypertension (HT) were unexpectedly more prevalent in the control group, and this difference was statistically significant (p=0.025). Among the general echocardiographic parameters, ejection fraction (EF), left atrium (LA), left ventricular end-diastolic diameter (LVED), left ventricular end-systolic diameter (LVES), posterior wall thickness (PW), and RV basal diameter showed no statistically significant differences between the two groups. Interventricular septum thickness and right atrial area were lower in the control group and statistically significant (p=0.032 and p=0.081, respectively). Parameters reflecting right ventricular systolic function, such as the LV/RV diameter ratio, TAPSE, S', systolic PAP (sPAP), RV FAC, and right ventricular index of myocardial performance (RIMP), showed no statistically significant differences between the two groups. Echocardiographic parameters reflecting right ventricular diastolic function, including triE, triA, triE/A, TE-E', triIVRT, triE', triA', triE/E', and triDT', showed no significant differences between the two groups. Conclusion: In conclusion, unlike the left ventricle, both systolic and diastolic functions of the right ventricle are not impaired in CSFP. However, there are studies with different results on this subject. Multicenter studies with larger patient populations are needed.