Instantaneous force-velocity-length relations in the intact human heart

On the flow field distortions due to the aortic arch twist

The aortic arch has, on average, an angle of twist of 15 degrees. The purpose of the research conducted was to ascertain if this twist angle has any effect on the flow field of the aortic arch and the distribution of the flow amongst the branches. It was found that the blood flow distribution is practically independent of the angle of twist of the aortic arch. However, the destination of a fluid particle located at a specific point in the cross-section at the entrance to the aortic arch does depend on the angle of twist.

Indices of ventricular contractile state: comparative sensitivity and specificity

Twenty-four indices of ventricular contractile state were compared as to inotropic sensitivity using dobutamine infusion, as well as to preload and afterload independence using dextran and phenylephrine infusion. Experiments were done in 10 open-chest instrumented dogs and signal processing was done off-line by digital techniques. The indices studied, listed in order of decreasing sensitivity, are (1) power-averaged rate of generation of power density, (2) peak isovolumic rate of change of power, (3) ejection rate of change of power at peak tension, (4) peak second time derivative of ventricular pressure, (5) peak ejection rate of change of power, (6) peak isovolumic power, (7) energy-averaged power density, (8) mean aortic blood acceleration, (9) peak aortic blood acceleration, (10) peak first time derivative of ventricular pressure, (11) peak normalized fiber velocity, (12) peak fiber velocity, (13) peak aortic blood flow, (14) peak power, (15) extrapolated Vmax (total pressure), (16) mean normalized fiber velocity, (17) mean fiber velocity, (18) extrapolated Vmax (developed pressure), (19) mean aortic blood flow, (20) mean power, (21) stroke volume, (22) peak wall tension, (23) mean wall tension, (24) time-tension index. The most sensitive index which was statistically independent of preload and afterload manipulation was the ejection rate of change of power at peak tension.

Quantitation of aortic insufficiency using a catheter-tip velocity transducer

Bidirectional instantaneous aortic root blood flow was measured in 18 patients with aortic insufficiency (AI) using a catheter-tip velocity transducer. The magnitude of AI was quantitated by determining total forward systolic flow from the area of the flow velocity curve above the zero baseline and regurgitant diastolic flow from the curve area below the baseline. Effective forward flow (stroke volume) was calculated as the difference between total forward systolic flow and regurgitant diastolic flow. Regurgitant fraction was determined as the ratio of regurgitant flow to total forward flow. These data were compared with conventional angiographic estimates (1+ to 4+) of the degree of insufficiency. Velocity transducer determination of regurgitant fraction was 26% in the patient with 1+ AI, 37% (31-48%) in 2+ AI, 49% (35-61%) in 3+ AI and 72% in 4+ AI (regurgitant fraction vs angiographic grade, r = 0.84). Regurgitant flow per diastole was 9 ml in the patient with 1+ AI, 39 ml (20-49 ml) in 2+ AI, 57 ml (31-102 ml) in 3+ AI and 183 ml (143 and 223 ml) in 4+ AI (regurgitant diastolic flow vs angiographic grade, r = 0.73). Good correlation (r = 0.90) was found between values of regurgitant flow obtained from the left ventriculogram and those obtained using the velocity transducer. Although the overall association was good, wide, variability in regurgitant fraction and regurgitant flow was found in the 15 patients with 2+ to 3+ AI. These results suggest that the electromagnetic velocity catheter offers a simple technique for quantitating AI.

Use of catheter-tip velocity--pressure transducer to evaluate left ventricular function in man: effects of intravenous propranolol

A catheter-tip velocity transducer with two high-fidelity pressure manometers was used to evaluate the left ventricular (LV) hemodynamic effects of intravenous propranolol (10 mg). Nine patients without clinical evidence of heart failure were studied. Pulsatile ascending aortic blood flow velocity and pressure and LV pressure were measured continuously during drug administration. Beat-to-beat changes in stroke volume index, stroke work index, LV end-diastolic pressure, maximum blood flow velocity and acceleration, and maximum LV dP/dt were determined. Propranolol produced a decrease in maximum blood flow velocity (from 58 +/- 4.7 to 42 +/- 5.1 cm/sec, p less than 0.002), and acceleration (from 1181 +/- 130 to 847 +/- 117 cm/sec2, p less than 0.002, max dP/dt (from 1361 +/- 70 to 1146 +/- 63 mm Hg/sec, p less than 0.002), stroke volume index (from 47 +/- 3.0 to 38 +/- 3.2 ml/m2, p less than 0.002) and total stroke work index (from 702 +/- 33 to 603 +/- 44 mJ/m2 p less than 0.04), with little change in mean aortic pressure, peak systolic pressure and LV end-diastolic pressure. Depression in myocardial function was detectable within 1 minute after initiation of propranolol and persisted when negative chronotropic effects were eliminated by atrial pacing. The multisensor catheter technique allows rapid and safe detection of changes in cardiovascular function during propranolol administration in conscious man.

Instantaneous blood flow responses to positive end-expiratory pressure with spontaneous ventilation

Variable hemodynamic responses to positive end-expiratory pressure (PEEP) with spontaneous ventilation have been reported. To clarify these responses, 15 awake patients were studied using a catheter-tip velocity transducer to record phasic aortic root blood flow continuously before, during and after PEEP (10 cm H2O) applied with a face mask. Central blood volume and effective ventricular filling pressures were measured. Phasic pulmonary artery blood flow was also simultaneously recorded in three of these patients. PEEP produced an acute aortic blood flow reduction, detected within one respiratory cycle. Stroke volume decreased 12%, and since heart rate was unchanged, cardiac output also declined (p less than 0.05). Inspiratory-to-expiratory aortic flow changes were less during PEEP. In contrast, inspiratory-to-expiratory pulmonary artery flow alterations were exaggerated due to a marked flow decline during expiration. Central blood volume and effective left ventricular filling pressure decreased 9% and 19%, respectively (p less than 0.05 in all patients). The decrease in pulmonary artery flow was associated with a decrease in central blood volume in the three patients in whom pulmonary flow was measured. PEEP promptly reduces cardiac output during spontaneous ventilation, related to a decrease in pulmonary flow in expiration.