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EXPERIMENTAL STUDY

Diastolic coronary vascular reserve: a new index to detect changes in the coronary microcirculation in hypertrophic cardiomyopathy

Rob Krams, MD, PhD^*,*, Folkert J. Ten Cate, MD, PhD, FACC, FESC^*, Stéphane G. Carlier, MD, PhD, A. F. W. van der Steen, PhD^* and Patrick W. Serruys, MD, PhD, FACC, FESC^*

^* Department of Cardiology, Thoraxcenter, Erasmus MC, Rotterdam, The Netherlands
Cardiovascular Center, OLV Hospital, Aalst, Belgium

Manuscript received June 3, 2003; revised manuscript received August 6, 2003, accepted September 9, 2003.

^* Reprint requests and correspondence: Dr. Rob Krams, Erasmus MC, Room Ee2369, Dr. Molewaterplein 40, 3015 GD Rotterdam, The Netherlands.
krams{at}erasmusmc.nl

OBJECTIVES: The present study introduces a modification of the diastolic coronary conductance concept that maintains its sensitive properties to detect changes in the coronary microcirculation in human hypertrophy.

BACKGROUND: Decrements of coronary flow in hypertrophy have been explained by changes in the coronary microcirculation. No measure is available to detect these changes.

METHODS: Doppler velocity catheters were introduced into the left anterior descending artery (LAD) and left circumflex coronary artery (LCx) of patients with obstructive hypertrophic cardiomyopathy (HCM) (n = 11) and into the LAD of cardiac transplant recipients (n = 9). The diastolic coronary conductance was measured at rest and after maximal hyperemia induced by a bolus injection of adenosine. Diastolic coronary vasodilator reserve (DCVR) was calculated as the hyperemic diastolic coronary conductance, divided by the coronary conductance during resting conditions.

RESULTS: Left ventricular outflow tract gradient in the HCM group (83 ± 31 mm Hg) was significantly higher (p < 0.05). Septal wall thickness was significantly increased (p < 0.05), while wall thickness was unchanged in the posterior wall of the HCM group. The coronary flow reserve was significantly decreased in the HCM-LCx region (to 64 ± 7% of control) and in the HCM-LAD regions (to 57 ± 7% of control). The DCVR was only decreased in the HCM-LAD (to 46 ± 3% of control) and not in the HCM-LCx group (86 ± 6%, p > 0.05). Esmolol did affect the pressure gradient and systolic shortening, but did not affect the maximal diastolic conductance.

CONCLUSIONS: The DCVR, in contrast with the coronary flow reserve, is decreased in those regions that display a disturbance in the microcirculation and may, therefore, offer a new way to study coronary adaptations in patients with hypertrophy.

Abbreviations and Acronyms   AUC = area under the curve   CFR = coronary flow reserve   DCVR = diastolic coronary vascular conductance reserve   HCM = hypertrophic cardiomyopathy   HTX = cardiac transplant recipients   LAD = left anterior descending coronary artery   LCx = left circumflex coronary artery   LV = left ventricular   QCA = quantitative coronary angiography   ROC = receiving operator curve

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