The Accuracy of the Electrocardiogram during Exercise Stress Test Based on Heart Size

BACKGROUND: Multiple studies have shown that the exercise electrocardiogram (ECG) is less accurate for predicting ischemia, especially in women, and there is additional evidence to suggest that heart size may affect its diagnostic accuracy. HYPOTHESIS: The purpose of this investigation was to assess the diagnostic accuracy of the exercise ECG based on heart size. METHODS: We evaluated 1,011 consecutive patients who were referred for an exercise nuclear stress test. Patients were divided into two groups: small heart size defined as left ventricular end diastolic volume (LVEDV) <65 mL (Group A) and normal heart size defined as LVEDV ≥65 mL (Group B) and associations between ECG outcome (false positive vs. no false positive) and heart size (small vs. normal) were analyzed using the Chi square test for independence, with a Yates continuity correction. LVEDV calculations were performed via a computer-processing algorithm. SPECT myocardial perfusion imaging was used as the gold standard for the presence of coronary artery disease (CAD). RESULTS: Small heart size was found in 142 patients, 123 female and 19 male patients. There was a significant association between ECG outcome and heart size (χ(2) = 4.7, p = 0.03), where smaller hearts were associated with a significantly greater number of false positives. CONCLUSIONS: This study suggests a possible explanation for the poor diagnostic accuracy of exercise stress testing, especially in women, as the overwhelming majority of patients with small heart size were women

Aficamten and Cardiopulmonary Exercise Test Performance

Importance Impaired exercise capacity is a cardinal manifestation of obstructive hypertrophic cardiomyopathy (HCM). The Phase 3 Trial to Evaluate the Efficacy and Safety of Aficamten Compared to Placebo in Adults With Symptomatic Obstructive HCM (SEQUOIA-HCM) is a pivotal study characterizing the treatment effect of aficamten, a next-in-class cardiac myosin inhibitor, on a comprehensive set of exercise performance and clinical measures. Objective To evaluate the effect of aficamten on exercise performance using cardiopulmonary exercise testing with a novel integrated measure of maximal and submaximal exercise performance and evaluate other exercise measures and clinical correlates. Design, Setting, and Participants This was a prespecified analysis from SEQUOIA-HCM, a double-blind, placebo-controlled, randomized clinical trial. Patients were recruited from 101 sites in 14 countries (North America, Europe, Israel, and China). Individuals with symptomatic obstructive HCM with objective exertional intolerance (peak oxygen uptake [pVO2] ≤90% predicted) were included in the analysis. Data were analyzed from January to March 2024. Interventions Randomized 1:1 to aficamten (5-20 mg daily) or matching placebo for 24 weeks. Main Outcomes and Measures The primary outcome was change from baseline to week 24 in integrated exercise performance, defined as the 2-component z score of pVO2 and ventilatory efficiency throughout exercise (minute ventilation [VE]/carbon dioxide output [VCO2] slope). Response rates for achieving clinically meaningful thresholds for change in pVO2 and correlations with clinical measures of treatment effect (health status, echocardiographic/cardiac biomarkers) were also assessed. Results Among 282 randomized patients (mean [SD] age, 59.1 [12.9] years; 115 female [40.8%], 167 male [59.2%]), 263 (93.3%) had core laboratory–validated exercise testing at baseline and week 24. Integrated composite exercise performance improved in the aficamten group (mean [SD] z score, 0.17 [0.51]) from baseline to week 24, whereas the placebo group deteriorated (mean [SD] z score, −0.19 [0.45]), yielding a placebo-corrected improvement of 0.35 (95% CI, 0.25-0.46; P &amp;amp;lt;.001). Further, aficamten treatment demonstrated significant improvements in total workload, circulatory power, exercise duration, heart rate reserve, peak heart rate, ventilatory efficiency, ventilatory power, and anaerobic threshold (all P &amp;amp;lt;.001). In the aficamten group, large improvements (≥3.0 mL/kg per minute) in pVO2 were more common than large reductions (32% and 2%, respectively) compared with placebo (16% and 11%, respectively). Improvements in both components of the primary outcome, pVO2 and VE/VCO2 slope throughout exercise, were significantly correlated with improvements in symptom burden and hemodynamics (all P &amp;amp;lt;.05). Conclusions and Relevance This prespecified analysis of the SEQUOIA-HCM randomized clinical trial found that aficamten treatment improved a broad range of exercise performance measures. These findings offer valuable insight into the therapeutic effects of aficamten. Trial Registration ClinicalTrials.gov Identifier: NCT0518681

Concomitant Aficamten and Disopyramide in Symptomatic Obstructive Hypertrophic Cardiomyopathy

Background Disopyramide, used in obstructive hypertrophic cardiomyopathy (oHCM) for its negative inotropic properties mediated by its reduction in cytosolic calcium, has been recommended for decades as an option to relieve resistant obstruction. Aficamten is a selective cardiac myosin inhibitor that reduces hypercontractility directly by reducing myosin-actin interaction. Objectives This study aims to investigate the safety and efficacy of concomitant use and withdrawal of disopyramide in patients with symptomatic oHCM receiving aficamten. Methods Patients with oHCM enrolled in REDWOOD-HCM Cohort 3 (open-label), SEQUOIA-HCM (placebo-controlled), and FOREST-HCM (open-label) were analyzed. The authors identified 4 groups, each with patients symptomatic despite background therapy with disopyramide who received: 1) disopyramide plus aficamten and subsequent aficamten withdrawal per protocol (Diso-Afi Withdrawal); 2) disopyramide plus placebo (Diso-Pbo); 3) aficamten plus disopyramide with subsequent disopyramide withdrawal (Afi-Diso Withdrawal); and 4) continued both disopyramide and aficamten (Diso+Afi Continuous). Assessments were performed at baseline, after aficamten or placebo add-on therapy, and after washout (except at week 24 for Diso+Afi Continuous group). Results Overall, 50 unique patients from 3 trials enrolled, resulting in 93 subjects (segments) across 4 groups: Diso-Afi Withdrawal (n = 29), Diso-Pbo (n = 20), Afi-Diso Withdrawal (n = 17), and Diso+Afi Continuous (n = 27); mean disopyramide dose was 331 ± 146 mg/d. The addition of aficamten to disopyramide alleviated left ventricular outflow tract (LVOT) obstruction (resting: change [Δ] in least squares mean −27.0 ± 3.6, Valsalva: Δ least squares mean −39.2 ± 5.0, both P < 0.0001), symptoms (≥1 NYHA functional class improvement: 77.8% [95% CI: 61.0-94.5]; P < 0.0001; Kansas City Cardiomyopathy Questionnaire–Clinical Summary Score: 12.3 ± 3.3 [P < 0.001]), and reduced N-terminal pro–B-type natriuretic peptide ratio: 0.35 [95% CI: 0.26-0.48]; P < 0.0001, and there was no significant change with placebo. Withdrawal of aficamten while on disopyramide resulted in return of LVOT obstruction, worsening of symptoms, and increase in NT-proBNP to baseline values. Conversely, withdrawal of disopyramide while on aficamten did not impact efficacy. There were no safety events associated with aficamten or disopyramide withdrawal, and no episodes of atrial fibrillation after disopyramide withdrawal. Conclusions In this cohort of patients with symptomatic oHCM with persistent LVOT obstruction, combination therapy with aficamten and disopyramide was safe and well tolerated but did not enhance clinical efficacy vs aficamten alone. For such oHCM patients, aficamten treatment may be considered with an option to discontinue disopyramide. (Dose-finding Study to Evaluate the Safety, Tolerability, PK, and PD of CK-3773274 in Adults With HCM [REDWOOD-HCM]; NCT04219826) (Aficamten vs Placebo in Adults With Symptomatic Obstructive Hypertrophic Cardiomyopathy [SEQUOIA-HCM]; NCT05186818) (Open-label Extension Study to Evaluate the Long-term Safety and Tolerability of Aficamten in Adults With HCM [FOREST-HCM]; NCT04848506