Cardiac Systolic and Diastolic Function in Relation to Cardiovascular Risk Factors: Comparing Strain Imaging in Russian and Norwegian Populations: Heart-to-Heart-Norwegian-Russian Multilevel Educational Collaboration in Cardiovascular Disease Epidemiology.

Background: Rates of cardiovascular morbidity and mortality are high in Russia. We compared conventional echocardiography and strain-based measures between Russian and Norwegian populations, and examined associations between hemodynamic and risk factors. Methods: Echocardiography was performed in 1192 participants from Arkhangelsk or Novosibirsk (Russia), and 917 from Tromsø (Norway), aged 40-69 years. "Normal" was defined as the absence of hypertension or cardiovascular disease. Conventional parameters and 2-dimensional speckle-tracking longitudinal strain and strain rate (systolic, early and late diastolic) were analyzed. Participants were categorized into 4 groups: normal, controlled hypertension, hypertensive blood pressure, and cardiac disease. Between-population comparisons used linear regression adjusted for prespecified covariates: age, sex, height, body mass index, blood pressure, heart rate, atrial fibrillation, smoking, pulmonary hypertension, and serum biomarkers (lipids, triglycerides, creatinine, high-sensitivity C-reactive protein, and HbA1c). Results: Russians showed a tendency toward lower longitudinal systolic functional indices, most evident in the normotensive group; however, these differences became nonsignificant after adjustment for hemodynamic and clinical covariates. Russians had lower stroke volume, higher heart rate, larger left atrial volume, and higher E/A ratio, indicating more impaired relaxation and elevated filling pressures. Groupwise comparisons (normal, controlled hypertension, hypertensive blood pressure, cardiac disease) showed that diastolic differences persisted after multivariable adjustment. Conclusions: After accounting for factors that influence cardiac function, systolic longitudinal strain parameters did not differ between Norwegian and Russian populations. In contrast, diastolic abnormalities persisted after adjustment, suggesting residual confounding and/or unmeasured determinants of diastolic dysfunction in the Russian population.