Anorexia Nervosa
This 19-year-old woman most likely has anorexia nervosa, as the constellation of cardiac muscle atrophy (smaller heart), prolonged QT interval, and bradycardia are the hallmark cardiovascular manifestations of prolonged starvation characteristic of this disorder.
Pathophysiology of Cardiac Changes in Anorexia Nervosa
Prolonged starvation in anorexia nervosa results in both anatomical and electrical cardiac abnormalities that directly explain this patient's presentation 1:
- Cardiac muscle atrophy occurs from chronic malnutrition, manifesting as a structurally smaller heart with reduced left ventricular mass 2, 3
- Sinus bradycardia develops from increased vagal tone as an adaptive response to starvation 1, 3, 4
- QTc interval prolongation results from the combined effects of malnutrition and concurrent electrolyte disturbances (hypokalemia, hypomagnesemia, hypocalcemia) 1, 5
Why Not the Other Eating Disorders?
Bulimia nervosa primarily causes cardiovascular complications through electrolyte imbalances from purging behaviors (vomiting, laxative abuse), but does not typically produce cardiac muscle atrophy or a smaller heart 6, 3. The structural cardiac changes seen in this patient point away from bulimia.
Binge-eating disorder is associated with obesity-related cardiac complications including cardiomegaly (enlarged heart), not a smaller heart 1. This is the opposite of what this patient demonstrates.
Pica and rumination disorder do not have well-established associations with the specific cardiac abnormalities described in this case 5.
Clinical Significance and Risk
Up to one-third of deaths in anorexia nervosa are cardiac-related, with sudden cardiac death being a frequent cause of mortality in this population 1. The mortality rate in anorexia nervosa ranges from 5-20%, with an actual rate likely around 6% 1.
Low weight, low body mass index, and rapid weight loss are the most important independent predictors of QTc interval prolongation in anorexia nervosa 1. This patient's combination of findings indicates significant medical compromise requiring immediate attention.
Reversibility with Treatment
Most cardiac manifestations of anorexia nervosa are completely reversible with appropriate nutritional rehabilitation 1, 5. This includes:
- Resolution of bradycardia 1
- Normalization of QTc intervals 1, 5
- Restoration of cardiac muscle mass 2, 3
- Resolution of pericardial effusions (another common finding in anorexia nervosa) 1, 2, 7
Critical Management Considerations
Carefully controlled refeeding is essential to reduce the risk of ventricular arrhythmias and sudden cardiac death, as overzealous refeeding can trigger the potentially fatal "refeeding syndrome" 1, 5, 8. Cardiac complications of refeeding syndrome typically occur within the first week and are associated with severe malnutrition (less than 70% ideal body weight) and hypophosphatemia 1, 8.
Prolonged, unbalanced, very low-calorie diets must be avoided as they may provoke life-threatening ventricular arrhythmias 1, 8.