title: Patterns of cardiac dysfunction coinciding with exertional breathlessness in hypertrophic cardiomyopathy.
abstract: OBJECTIVE
  The commonest cause of breathlessness in hypertrophic cardiomyopathy (HCM) is left ventricular outflow tract (LVOT) obstruction which improves with its removal. However, in the absence of outflow tract obstruction, as in dilated cardiomyopathy, patients may be limited by similar symptoms, thus suggesting a potential common mechanism for the two conditions. We aimed to assess cardiac function at the time of symptoms in a group of unselected patients with HCM to identify other patterns of cardiac dysfunction which coincide with their breathlessness.
  
  
  METHODS
  We studied 37 HCM patients (aged 55 ± 15 years, 13 female) with septal thickness >15 mm and 17 controls (aged 58 ± 12 years, 12 female) using Doppler echocardiography, at rest and at peak dobutamine stress. Stress end points were symptoms, >20 mmHg drop in systolic blood pressure, arrhythmia, or maximum dobutamine dosage of 40 μg/kg/min.
  
  
  RESULTS
  At rest: LV systolic function was maintained (EF 68 ± 7 v 76 ± 12%, respectively), LVOT velocity raised (p<0.005), lateral and septal long axis amplitude reduced (p<0.05 and p<0.005, respectively) and dyssynchronous and QRS duration was also broader (p<0.005) in patients compared to controls. At peak stress: Overall LVOT velocities were higher in patients than controls (4.3 ± 1.7 v 1.7 ± 1.0m/s, p<0.005, respectively) due to systolic anterior movement of the mitral valve and mitral regurgitation developing. In the 15 patients who did not develop significant LVOT obstruction (velocity <4m/s), LV ejection time increased and peak systolic amplitude did not increase. In the 10 patients with neither LVOT obstruction nor restrictive filling, QRS duration prolonged by 12 ms (p <0.05), post-ejection shortening worsened and peak systolic amplitude fell (p<0.005). Also, LV ejection time prolonged by 5s/min (p<0.05), filling time failed to increase as it did in controls (p<0.005) and Tei index was higher than controls (p<0.01).
  
  
  CONCLUSIONS
  Exertional breathlessness in HCM is associated with LV outflow tract obstruction and functional mitral regurgitation in almost two thirds of patients. The remaining one third have either resistant restrictive physiology or dyssynchronous cavity at fast heart rate. Despite similar exercise limiting breathlessness in the three groups, means of management should be quite different.
authors.affiliation: Canterbury Christ Church University, Canterbury, UK.
authors.forename: Dejan
authors.initials: D
authors.lastname: Maras
authors.forename: Robin
authors.initials: R
authors.lastname: Chung
authors.forename: Alison
authors.initials: A
authors.lastname: Duncan
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Christine
authors.initials: C
authors.lastname: Thorp
authors.forename: Stellan
authors.initials: S
authors.lastname: Mörner
authors.forename: Per
authors.initials: P
authors.lastname: Lindqvist
authors.forename: Michael Y
authors.initials: MY
authors.lastname: Henein
mesh_terms: D000328:Adult; D000368:Aged; D001794:Blood Pressure; D058406:Cardiac Resynchronization Therapy; D002312:Cardiomyopathy, Hypertrophic / Q000150:complications* / Q000000981:diagnostic imaging* / Q000628:therapy; D002316:Cardiotonic Agents; D004280:Dobutamine; D004417:Dyspnea / Q000209:etiology*; D005080:Exercise Test / Q000379:methods; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D008944:Mitral Valve Insufficiency / Q000150:complications* / Q000000981:diagnostic imaging; D013599:Systole; D018608:Ultrasonography, Doppler; D018487:Ventricular Dysfunction, Left / Q000150:complications / Q000000981:diagnostic imaging / Q000628:therapy; D014694:Ventricular Outflow Obstruction / Q000150:complications* / Q000000981:diagnostic imaging / Q000628:therapy
chemical_list: D002316:Cardiotonic Agents; D004280:Dobutamine
keywords: Cardiac resynchronization therapy; Dynamic LVOT obstruction; Exertional dyspnea; Stress echocardiography; Systolic anterior motion