title: Myocardial blood flow and left ventricular functional reserve in hypertrophic cardiomyopathy: a13NH3gated PET study.
abstract: BACKGROUND
  Ischemia in hypertrophic cardiomyopathy (HCM) is caused by coronary microvascular dysfunction (CMD), which is detected by measuring myocardial blood flow (MBF) with PET. Whether CMD may be associated with ischemic left ventricular (LV) dysfunction is unclear. We therefore assessed LV ejection fraction (EF) reserve in HCM patients undergoing dipyridamole (Dip) PET.
  
  
  METHODS
  Resting and stress13NH3dynamic as well as gated PET were performed in 34 HCM patients. Segmental MBF and transmural perfusion gradient (TPG = subendocardial / subepicardial MBF) were assessed. LVEF reserve was considered abnormal if Dip LVEF decreased more than 5 units as compared to rest.
  
  
  RESULTS
  Eighteen patients had preserved (group A) and 16 abnormal LVEF reserve (group B; range -7 to -32). Group B patients had greater wall thickness than group A, but resting volumes, LVEF, resting and Dip MBF, and myocardial flow reserve were similar. Group B had slightly higher summed stress score and summed difference score in visual analysis than group A, and a significantly higher summed stress wall motion score. In group B, resting TPG was slightly lower (1.31 ± 0.29 vs. 1.37 ± 0.34, p <0.05), and further decreased after Dip, whilst in group A it increased (B = 1.20 ± 0.39, p < 0.0001 vs. rest and vs. A = 1.40 ± 0.43). The number of segments per patient with TPG <1 was higher than in group A (p < 0.001) and was a significant predictor of impaired LVEF reserve (OR 1.86, p < 0.02), together with wall thickness (OR 1.3, p < 0.02).
  
  
  CONCLUSIONS
  Abnormal LVEF response is common in HCM patients following Dip, and is related to abnormal TPG, suggesting that subendocardial ischemia might occur under Dip and cause transient LV dysfunction. Although in vivo this effect may be hindered by the adrenergic drive associated with effort, these findings may have relevance in understanding exercise limitation and heart failure symptoms in HCM.
authors.affiliation: Nuclear Medicine Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Largo Brambilla 3, 50134, Florence, Italy. roberto.sciagra@unifi.it.
authors.forename: Roberto
authors.initials: R
authors.lastname: Sciagrà
authors.affiliation: Nuclear Medicine Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Largo Brambilla 3, 50134, Florence, Italy.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Calabretta
authors.affiliation: Department of Statistics, University of Florence, Florence, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Cipollini
authors.affiliation: Nuclear Medicine Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Largo Brambilla 3, 50134, Florence, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Passeri
authors.affiliation: Nuclear Medicine Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Largo Brambilla 3, 50134, Florence, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Castello
authors.affiliation: Referral Centre for Myocardial Diseases, Careggi University Hospital, Florence, Italy.
authors.forename: Franco
authors.initials: F
authors.lastname: Cecchi
authors.affiliation: Referral Centre for Myocardial Diseases, Careggi University Hospital, Florence, Italy.
authors.forename: Iacopo
authors.initials: I
authors.lastname: Olivotto
authors.affiliation: Nuclear Medicine Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Largo Brambilla 3, 50134, Florence, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Pupi
mesh_terms: D000328:Adult; D064751:Ammonium Compounds; D055424:Cardiac-Gated Imaging Techniques; D002312:Cardiomyopathy, Hypertrophic / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D003326:Coronary Circulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009590:Nitrogen Radioisotopes; D049268:Positron-Emission Tomography; D013318:Stroke Volume; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging*
chemical_list: D064751:Ammonium Compounds; D009590:Nitrogen Radioisotopes
keywords: Hypertrophic Cardiomyopathy; Left Ventricular Ejection Fraction; Myocardial Blood Flow; N-13-Ammonia; Positron Emission Tomography