SummaryBackground: The clinical accuracy of myocardial contrast echocardiography (MCE) using intermittent harmonic imaging and intravenous perfluorocarbon containing microbubbles during dipyridamole stress has not been evaluated in a multicenter setting.Hypothesis: The accuracy of dipyridamole stress contrast echo in the detection of coronary artery disease (CAD) using myocardial perfusion images is high in comparison with technetium-99 ( 99 Tc) sestamibi single-photon emission computed tomography (MIBI SPECT) and increases the accuracy of wall motion data.Methods: In 68 consecutive nonselected patients (46 men; mean age 66 years) from three different institutions in two countries, dipyridamole stress echo and SPECT with 99m Tc MIBI were compared. Continuous intravenous (IV) infusion of perfluorocarbon exposed sonicated dextrose albumin (PES-DA) (2-5 cc/min) was administered for baseline myocardial perfusion using triggered harmonic end systolic frames. Realtime digitized images were used for wall motion analysis. Dipyridamole was then injected in two steps: (1) 0.56 mg/kg for 3 min; (2) 0.28 mg/kg for 1 min, if the first step was negative for an inducible wall motion abnormality. After dipyri-

SummaryBackground: Adjunctive isometric exercise in the form of sustained submaximal handgrip (HG) is considered to increase the sensitivity of dobutamine stress echo (DSE) for detection of functionally significant coronary artery disease.Hypothesis: The study was undertaken to quantify invasively the impact of HG in humans on hemodynamics and myocardial oxygen consumption (MVO2) during DSE.Methods: An invasive hemodynamic evaluation was performed during DSE and with addition of adjunctive HG in 11 subjects. Coronary sinus (CS) blood flow, right-sided and systemic pressures, oxygen saturations, and transthoracic two-dimensional echocardiography were obtained at each 3-min stage and after adding HG at peak DSE. Myocardial oxygen consumption was calculated by the Fick method and circumferential end-systolic wall stress (ESWS) by Mirsky's formula.Results: At peak DSE, heart rate, left ventricular ejection fraction, CS flow, and MVO2 increased, whereas pulmonary capillary wedge pressure (PCWP) and circumferential endsystolic wall stress (ESWS) decreased from baseline. Com-

To change the stretch on cardiopulmonary mechanoreceptors, large shifts of blood in the capacity space were elicited by tilting and by exerting positive lower body pressure in the tilted position. Twelve volunteers underwent invasive hemodynamic studies and in 10 other subjects cardiac size was determined by radionuclide cardiography. In all 22 subjects tilting caused the expected increase of renin, which was abolished by lower body compression. Decompression caused renin to increase again. Right atrial pressure in invasive studies and end-systolic and end-diastolic counts in noninvasive studies showed a significant and strong negative correlation with renin and norepinephrine levels. Thus, the degree of stretch of the cardiopulmonary mechanoreceptors is a major determinant of reflex regulation of renin release in humans.