Extreme Asymmetric Septal Hypertrophy with Fibrosis Leading to Sudden Cardiac Arrest

Presenting Author(s)

• 

  Mariano Domanico, MD

  Cardiologist, Department of Cardiac Imaging, Hosptital Bicentenario Esteban Echeverria
  Hospital del Bicentenario Esteban Echeverria
  Caba, Buenos Aires, Argentina

Primary Author(s)

• 

  Mariano Domanico, MD

  Cardiologist, Department of Cardiac Imaging, Hosptital Bicentenario Esteban Echeverria
  Hospital del Bicentenario Esteban Echeverria
  Caba, Buenos Aires, Argentina

Co-Author(s)

• PK

  Pablo Kociubinski, MD

  Cardiologist, Department of Cardiac Imaging, Hosptital Bicentenario Esteban Echeverria
  Hosptital Bicentenario Esteban Echeverria, Argentina
• FV

  Florencia Vago, BSc

  Bachelor in Medical Imaging Production
  Hospital Bicentenario de Esteban Echeverria, Argentina
• LD

  Leonardo Del Rio, MD

  Chief of Cardiology, Hospital Bicentenario de Esteban Echeverría
  Hospital Bicentenario de Esteban Echeverria, Argentina
• UR

  Ulises Rebelo, MD

  Cardiologist, Department of Cardiac Imaging, Hosptital Bicentenario Esteban Echeverria
  Hosptital Bicentenario Esteban Echeverria, Argentina
• JG

  Juan Pablo Guzman, MD

  Staff Cardiologist, Hospital Bicentenario de Esteban Echeverría
  Hospital Bicentenario de Esteban Echeverría, Argentina
• MA

  Matias Anchorena, MD

  Staff Cardiologist, Hospital Bicentenario de Esteban Echeverría
  Hospital del Bicentenario Esteban Echeverria, Argentina
• CN

  Christian Nissen, MD

  Head of the Imaging Department, Hospital Bicentenario de Esteban Echeverría
  Hospital Bicentenario de Esteban Echeverría, Argentina
• PC

  Pablo Centeno, MD

  Chief of Cardiology, Hospital Bicentenario de Esteban Echeverría
  Hospital del Bicentenaria Esteban Echeverria, Argentina
• EL

  Eduardo Lucchesi, MD

  Medical Director of the Hospital del Bicentenario of Esteban Echeverría
  Hospital del Bicentenario de Esteban Echeverria, Argentina

Description of Clinical Presentation: A 42-year-old woman with no relevant medical or family history was admitted with a three-month history of progressive exertional dyspnea, which had worsened in recent weeks, associated with palpitations and a syncopal episode while climbing stairs. During hospitalization, she developed sustained ventricular tachycardia progressing to cardiac arrest, successfully resuscitated with advanced life support. Transthoracic echocardiography revealed a nondilated left ventricle with preserved systolic function and a basal septal thickness of 22 mm, with evidence of dynamic LVOT obstruction at rest and a mild posteriorly directed mitral regurgitant jet.

Diagnostic Techniques and Their Most Important Findings: Cardiac magnetic resonance (CMR) demonstrated a nondilated left ventricle with preserved global systolic function but markedly increased myocardial mass due to severe asymmetric hypertrophy. Hypertrophy predominantly involved the septum (basal, mid, and apical), with extension into the anterior wall and the inferior wall at mid and apical levels. Maximal wall thickness was observed in the mid-inferoseptal segment (36.5 mm) and the septoapical segment (32 mm). Additional morphological features included papillary muscle hypertrophy, significant trabeculation, and systolic cavity obliteration—complete at the apex and partial at the mid-ventricular level. Late gadolinium enhancement (LGE) revealed extensive intramyocardial fibrosis with a confluent, non-ischemic pattern, most pronounced in the mid-anteroseptal (sg8) and basal anteroseptal (sg2) segments, with an additional focus at the inferoseptal–inferior junction (sg9–10). This pattern is characteristic of hypertrophic cardiomyopathy and represents a structural substrate for ventricular arrhythmogenesis.

Learning Points from this Case: Cardiac magnetic resonance (CMR) provided a comprehensive morphological assessment, revealing extreme asymmetric septal hypertrophy (maximum wall thickness 36.5 mm) extending into the anterior and inferior walls, accompanied by papillary muscle hypertrophy and apical obliteration. Detailed segmental quantification of myocardial thickness is essential to capture the heterogeneous distribution of hypertrophy beyond a single maximal measurement. The presence of extensive intramyocardial fibrosis on LGE (10%) is a well-recognized marker of adverse prognosis and is strongly associated with arrhythmic events. The patient’s clinical course, characterized by syncope and cardiac arrest, together with these imaging findings, led to implantation of an implantable cardioverter-defibrillator (ICD) for secondary prevention of sudden cardiac death.

Cardiac magnetic resonance cine images (short-axis and long-axis views) showing marked asymmetric septal hypertrophy with apical cavity obliteration.
Late gadolinium enhancement (LGE) image showing intramyocardial fibrosis with a confluent non-ischemic pattern in the septum.
Segmental wall thickness map (bull’s eye) demonstrating maximal hypertrophy in the mid-inferoseptal (36.5 mm), septoapical (32 mm), and basal anteroseptal (31.6 mm) segments.