Myocardial blood flow and left ventricular functional reserve in hypertrophic cardiomyopathy: a 13NH3 gated PET study

Roberto Sciagrà; Raffaella Calabretta; Fabrizio Cipollini; Alessandro Passeri; Angelo Castello; Franco Cecchi; Iacopo Olivotto; Alberto Pupi

doi:10.1007/s00259-016-3603-2

Myocardial blood flow and left ventricular functional reserve in hypertrophic cardiomyopathy: a ¹³NH₃ gated PET study

Eur J Nucl Med Mol Imaging. 2017 May;44(5):866-875. doi: 10.1007/s00259-016-3603-2. Epub 2017 Jan 3.

Authors

Roberto Sciagrà¹, Raffaella Calabretta², Fabrizio Cipollini³, Alessandro Passeri², Angelo Castello², Franco Cecchi⁴, Iacopo Olivotto⁴, Alberto Pupi²

Affiliations

¹ 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.
² Nuclear Medicine Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Largo Brambilla 3, 50134, Florence, Italy.
³ Department of Statistics, University of Florence, Florence, Italy.
⁴ Referral Centre for Myocardial Diseases, Careggi University Hospital, Florence, Italy.

PMID: 28050630
DOI: 10.1007/s00259-016-3603-2

Abstract

Introduction: 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 stress ¹³NH₃ dynamic 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).

Conclusion: 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.

Keywords: Hypertrophic Cardiomyopathy; Left Ventricular Ejection Fraction; Myocardial Blood Flow; N-13-Ammonia; Positron Emission Tomography.

MeSH terms

Adult
Ammonium Compounds*
Cardiac-Gated Imaging Techniques*
Cardiomyopathy, Hypertrophic / diagnostic imaging*
Cardiomyopathy, Hypertrophic / physiopathology*
Coronary Circulation*
Female
Humans
Male
Middle Aged
Nitrogen Radioisotopes
Positron-Emission Tomography*
Stroke Volume
Ventricular Dysfunction, Left / diagnostic imaging*

Substances

Ammonium Compounds
Nitrogen Radioisotopes