{
  "abstract": "Introduction Atrioventricular (AV) nodal disease is a rare but serious complication of hypertrophic cardiomyopathy (HCM), often leading to conduction abnormalities. While atrial fibrillation is common, high-degree AV block (AVB) is rare. We present a case of hypertrophic obstructive cardiomyopathy (HOCM) complicated by ventricular standstill, emphasizing the need for early recognition and management.Case Presentation A 46-year-old man with a family history of HCM (mother with ICD) presented with exertional dyspnea, palpitations, and presyncope for six months. No family history of sudden cardiac death. Examination revealed HR 76 bpm, BP 115/75 mmHg, and an ejection systolic murmur. ECG showed ventricular hypertrophy, dagger-shaped Q waves, T-wave inversions, first-degree AVB (280 ms), and ventricular ectopics ( figures 1 and 2). Troponin and NT-proBNP were elevated.Echocardiography confirmed HOCM with severe septal hypertrophy, a maximal LVOT gradient of 43 mmHg, and systolic anterior motion of the mitral valve. Indexed left atrial volume was 48 mL/m2 (figures 3 and 4). CT coronary angiogram was normal.He was started on bisoprolol 2.5 mg OD and within 48 hours developed intermittent high-degree AVB (2:1, 3:1). Bisoprolol was discontinued due to worsening conduction abnormalities, but he later developed symptomatic complete heart block, necessitating emergency ICD placement (figure 5).He was started on bisoprolol 2.5 mg OD and within 48 hours developed intermittent high-degree AVB (2:1, 3:1). Bisoprolol was discontinued due to worsening conduction abnormalities, but he later developed symptomatic complete heart block, necessitating emergency ICD placement.Abstract 1-035 Figure 1Cardiac tape showing 2:1 and 3:1 AV blockAbstract 1-035 Figure 2Cardiac tape showing first degree AV blockAbstract 1-035 Figure 3Apical 4-chamber view showing LV hypertrophyAbstract 1-035 Figure 4PLAX view showing significantly thickened myocardiumAbstract 1-035 Figure 5Chest x-ray following pacing and ICD insertionDiscussion HCM is the most common genetic heart disease, inherited in an autosomal dominant manner in 50% of cases. MYBPC3 mutations are frequently linked to high-degree AV block. 1 While atrial fibrillation is common in HCM, high-degree AV block remains rare.First-degree AVB in HCM is increasingly recognized as a marker of disease progression and arrhythmic risk.1 Mechanisms include left atrial enlargement (predisposing to atrial fibrillation and thromboembolism) and myocardial fibrosis, promoting electrical instability.1 Our patient had a 3.1% five-year sudden cardiac death risk and developed high-degree AV block and ventricular standstill. This progression was likely exacerbated by bisoprolol, which slowed AV conduction in the setting of pre-existing first-degree AV block. Beta-blockers, though essential in HCM management, should be used cautiously in patients with conduction abnormalities.This case underscores the need for personalized HCM management. First-degree AVB may identify high-risk individuals requiring closer monitoring, medication adjustments, and early device therapy.Conclusion High-degree AV block and ventricular standstill are rare but significant complications of HCM. First-degree AVB may serve as an early risk marker linked to left atrial enlargement, fibrosis, and arrhythmias. Clinicians should monitor conduction abnormalities closely, especially when prescribing AV-slowing medications. Genetic evaluation, surveillance, and individualized treatment strategies are crucial for optimizing outcomes in HCM patients.Reference Higuchi S, Liu K, Ling LH, Sy RW, Mulpuru SK, Vatury O, Callans DJ, Garcia FC, Epstein LM, Kumar UN. Prognostic implications of first-degree atrioventricular block associated with hypertrophic cardiomyopathy. Journal of the American Heart Association 2020;9(5):e015064. https://doi.org/10.1161/JAHA.119.015064",
  "authors": [
    {
      "affiliations": [
        "The Shrewsbury and Telford Hospital NHS Trust, UK"
      ],
      "name": "Olasunkanmi H Owolabi"
    },
    {
      "affiliations": [
        "The Shrewsbury and Telford Hospital NHS Trust, UK"
      ],
      "name": "Hassan O Yera"
    },
    {
      "affiliations": [
        "The Shrewsbury and Telford Hospital NHS Trust, UK"
      ],
      "name": "Chern H Choy"
    },
    {
      "affiliations": [
        "The Shrewsbury and Telford Hospital NHS Trust, UK"
      ],
      "name": "Kaung Htet"
    },
    {
      "affiliations": [
        "The Shrewsbury and Telford Hospital NHS Trust, UK"
      ],
      "name": "Suman Kundu"
    }
  ],
  "title": "1-035 A case of ventricular standstill in hypertrophic cardiomyopathy: the role of AV block and beta-blockers",
  "uid": "6125e68e-79c1-568b-b965-8a829c75777e"
}