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Assessment of peripheral artery tonometry in the detection of treadmill exercise-induced myocardial ischemia

Pierre Chouraqui, MD, FACC^*,*, Robert P. Schnall, DSc, Itsik Dvir, DSc, Alan Rozanski, MD, FACC, Ehtasham Qureshi, MD, Alexander Arditti, MD, Jerold Saef, MD, FACC^||, Paul D. Feigin, PhD^¶ and Jacob Sheffy, PhD

^* Nuclear Cardiology Unit, The Heart Institute, Chaim Sheba Medical Center, Tel Hashomer, and the Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
Itamar Medical Ltd., Caesarea, Israel
Department of Medicine, St. Luke’s-Roosevelt Hospital, New York, New York, USA
The Heart Institute, Kaplan Medical Center, Rehovot, Israel
^|| Batey Cardiovascular Center, Bradenton, Florida, USA
^¶ Faculty of Industrial Engineering and Management, Technion, Israel Institute of Technology, Haifa, Israel

View larger version (31K): [in a new window]   Figure 1 Schematic diagram of the sensor’s structure. The sensor is partitioned into two separate sections that are independently pressurized. The sensor cap has a split thimble design that imparts a two-point clamping effect to lock the sensor to the finger tip while measuring pulsatile volume changes. The adjacent open-ended annular cuff provides a buffering effect against retrograde shock waves, to reduce noise, but is not used for sensing. Both compartments are designed to keep the venous transmural pressure negative to prevent venous pooling and distention and to ensure that only arterial volume changes are recorded.

View larger version (26K): [in a new window]   Figure 2 Representative examples of the peripheral arterial tonometer (PAT) signal’s time course in PAT-normal and PAT-abnormal cases. (Upper tracing) A negative PAT responder showing the typical progressive increase in the signal throughout exercise. (Lower tracing) A progressive decrease in PAT signal amplitude, which was the hallmark of the vasoconstrictive response, representing a typical abnormal PAT response. Inserts show higher resolution samples at the start and end of exercise periods.

View larger version (17K): [in a new window]   Figure 3 (Thickest curve) The receiver-operating characteristic (ROC) curve for the validation sample of 616 subjects in whom the peripheral arterial tonometer (PAT) outcome was used in combination with the electrocardiograph (ECG) result (PAT enhanced). The area under the curve (AUC) was 0.72. At a specificity value of 67.8%, the sensitivity of the combined PAT and ECG model was 62.4%, compared with 44.7% for ECG alone (p < 0.0001). The specificity value selected represents the specificity value of ECG for this study population. (Thinner curve) The ROC curve for the validation sample of 616 subjects in whom only the PAT outcome (PAT alone) was used. The AUC was 0.675. At a specificity value of 67.8%, the sensitivity of PAT was 58.4%, compared with 44.7% for ECG alone (p < 0.01).