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Background: In patients with hypertrophic cardiomyopathy (HCM), impaired augmentation of stroke volume and diastolic dysfunction contribute to exercise intolerance. Systolic–diastolic (S‐D) coupling characterizes how systolic contraction of the left ventricle (LV) primes efficient elastic recoil during early diastole. Impaired S‐D coupling may contribute to the impaired cardiac response to exercise in patients with HCM. Methods: Patients with HCM (n = 25, age = 47 ± 9 years) and healthy adults (n = 115, age = 49 ± 10 years) underwent a cardiopulmonary exercise testing (CPET) and echocardiogram. S‐D coupling was defined as the ratio of LV longitudinal excursion of the mitral annulus during early diastole (EDexc) and systole (Sexc) and compared between groups. Peak oxygen uptake (peak V̇O2) (Douglas bags), cardiac index (C2H2 rebreathe), and stroke volume index (SVi) were assessed during CPET. Linear regression was performed between S‐D coupling and peak V̇O2, peak cardiac index, and peak SVi. Results: S‐D coupling was lower in HCM (Controls: 0.63 ± 0.08, HCM: 0.56 ± 0.10, p < 0.001). Peak V̇O2 and stroke volume reserve were lower in patients with HCM (Peak VO2 Controls: 28.5 ± 5.5, HCM: 23.7 ± 7.2 mL/kg/min, p < 0.001, SV reserve: Controls 39 ± 16, HCM 30 ± 18 mL, p = 0.008). In patients with HCM, S‐D coupling was associated with peak V̇O2 (r = 0.47, p = 0.018), peak cardiac index (r = 0.60, p = 0.002), and peak SVi (r = 0.63, p < 0.001). Conclusion: Systolic–diastolic coupling was impaired in patients with HCM and was associated with fitness and the cardiac response to exercise. Inefficient S‐D coupling may link insufficient stroke volume generation, diastolic dysfunction, and exercise intolerance in HCM. [ABSTRACT FROM AUTHOR]

BACKGROUND: Despite advances in medical and cardiac resynchronization therapy (CRT), individuals with chronic congestive heart failure (CHF) have persistent symptoms, including exercise intolerance. Optimizing cardio-locomotor coupling may increase stroke volume and skeletal muscle perfusion as previously shown in healthy runners. Therefore, we tested the hypothesis that exercise stroke volume and cardiac output would be higher during fixed-paced walking when steps were synchronized with the diastolic compared with systolic portion of the cardiac cycle in patients with CHF and CRT. METHODS: Ten participants (58±17 years of age; 40% female) with CHF and previously implanted CRT pacemakers completed 5-minute bouts of walking on a treadmill (range, 1.5--3 mph). Participants were randomly assigned to first walking to an auditory tone to synchronize their foot strike to either the systolic (0% or 100±15% of the R-R interval) or diastolic phase (45±15% of the R-R interval) of their cardiac cycle and underwent assessments of oxygen uptake (V-o2; indirect calorimetry) and cardiac output (acetylene rebreathing). Data were compared through paired-samples t tests. RESULTS: V-o2 was similar between conditions (diastolic 1.02±0.44 versus systolic 1.05±0.42 L/min; P=0.299). Compared with systolic walking, stroke volume (diastolic 80±28 versus systolic 74±26 mL; P=0.003) and cardiac output (8.3±3.5 versus 7.9±3.4 L/min; P=0.004) were higher during diastolic walking; heart rate (paced) was not different between conditions. Mean arterial pressure was significantly lower during diastolic walking (85±12 versus 98±20 mm Hg; P=0.007). CONCLUSIONS: In patients with CHF who have received CRT, diastolic stepping increases stroke volume and oxygen delivery and decreases afterload. We speculate that, if added to pacemakers, this cardio-locomotor coupling technology may maximize CRT efficiency and increase exercise participation and quality of life in patients with CHF. [ABSTRACT FROM AUTHOR]