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CLINICAL RESEARCH: ENHANCED EXTERNAL COUNTERPULSATION

Enhanced External Counterpulsation Treatment Improves Arterial Wall Properties and Wave Reflection Characteristics in Patients With Refractory Angina

Department of Medicine/Cardiology, University of Florida College of Medicine, Gainesville, Florida.

Manuscript received February 2, 2006; revised manuscript received April 19, 2006, accepted April 24, 2006.

^_* Reprint requests and correspondence: Wilmer W. Nichols, PhD, Department of Medicine/Cardiology, Box 100277, University of Florida, Gainesville, Florida 32610. (Email: nichoww{at}medicine.ufl.edu).

OBJECTIVES: To determine if arterial properties and wave reflection characteristics are favorably altered after enhanced external counterpulsation (EECP) treatment in patients with refractory angina.

BACKGROUND: Early return of reflected waves from the lower body, resulting from increased arterial stiffness, augments central aortic pressure and increases left ventricular (LV) afterload and myocardial oxygen demand. EECP acutely enhances coronary perfusion (supply) and reduces LV afterload (demand). However, the mechanisms responsible for the sustained beneficial effects of EECP treatment are unclear.

METHODS: Radial artery pressure waveforms were recorded by applanation tonometry and central aortic pressure waveforms generated using a mathematical transfer function in 20 patients with stable refractory angina. Data were collected before and after 34 1-h EECP sessions. Augmentation index (AI_a) and timing of the reflected pressure wave were calculated from the aortic waveform.

RESULTS: EECP treatment caused a decline in AI_a and an increase in reflected wave travel time. These modifications in wave reflection characteristics caused a decrease in aortic systolic pressure and wasted LV pressure energy. The average number of angina episodes and Canadian Cardiovascular Society (CCS) class, both decreased in concordance with the physiologic changes due to EECP treatment.

CONCLUSIONS: EECP treatment reduces arterial stiffness and improves wave reflection characteristics in patients with refractory angina. These changes decrease LV afterload and myocardial oxygen demand and reduce the number of angina episodes, therefore enabling patients to participate in continuous exercise programs which in turn may provide long-term benefits and sustained improved quality of life.

Abbreviations and Acronyms   AIa = augmentation index   CAD = coronary artery disease   CCS = Canadian Cardiovascular Society   tp = round trip travel time of the pressure wave from the heart to the periphery and back   tp/2 = one-way travel time of the reflected pressure wave from the periphery to the heart   tr = systolic duration of the reflected wave   EECP = enhanced external counterpulsation   LV = left ventricular   NO = nitric oxide   TTI = tension-time index

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