Effectiveness of a new diagnostic algorithm for the diagnosis of unexplained syncope in patients with hypertrophic cardiomyopathy

Background: In patients with hypertrophic cardiomyopathy (HCM), identifying the underlying mechanism of unexplained syncope is crucial for preventing sudden cardiac death (SCD) and managing recurrences. We evaluated the effectiveness of a novel stepwise diagnostic algorithm for the etiological assessment of syncope in a clinical HCM cohort. Methods: We retrospectively applied the algorithm to consecutive HCM patients with unexplained syncope referred to the Syncope or Cardiomyopathy Units at Careggi University Hospital (Florence, Italy) between May 2004 and July 2024. Results: Among 43 patients (mean age 54.9 ± 17.4 years; 56% male), the cause of syncope was identified at Step 1 (initial evaluation) in 22 cases (51.2%): hypotensive in 18 and arrhythmic in 4. An obstructive mechanism (LVOTO) was the primary cause in 1 additional case (2.3%). Autonomic assessment (Step 3: Tilt Testing, Carotid Sinus Massage, and ABPM) provided diagnostic findings in 11 patients (25.5%). Implantable Loop Recorders (ILR, Step 4) were deployed in 13 patients (30.2%), revealing significant asystole in 2 (15.3%) and excluding arrhythmia in 1 (7.6%) during recurrences. Overall, the algorithm established a diagnosis in 88.3% of cases. Over a mean follow-up of 82.8 ± 50.6 months, no SCD occurred; 6 patients received an ICD. Conclusion: A structured, stepwise diagnostic approach clarified the cause of syncope in nearly 90% of HCM patients, potentially optimizing long-term risk stratification and reducing unnecessary device implantation.