Hemodynamic correlates of left ventricular versus right ventricular radionuclide volumetric responses to vasodilator therapy in congestive heart failure secondary to ischemic or dilated cardiomyopathy

Validation of subject-specific cardiovascular system models from porcine measurements

A previously validated mathematical model of the cardiovascular system (CVS) is made subject-specific using an iterative, proportional gain-based identification method. Prior works utilised a complete set of experimentally measured data that is not clinically typical or applicable. In this paper, parameters are identified using proportional gain-based control and a minimal, clinically available set of measurements. The new method makes use of several intermediary steps through identification of smaller compartmental models of CVS to reduce the number of parameters identified simultaneously and increase the convergence stability of the method. This new, clinically relevant, minimal measurement approach is validated using a porcine model of acute pulmonary embolism (APE). Trials were performed on five pigs, each inserted with three autologous blood clots of decreasing size over a period of four to five hours. All experiments were reviewed and approved by the Ethics Committee of the Medical Faculty at the University of Liege, Belgium. Continuous aortic and pulmonary artery pressures (P(ao), P(pa)) were measured along with left and right ventricle pressure and volume waveforms. Subject-specific CVS models were identified from global end diastolic volume (GEDV), stroke volume (SV), P(ao), and P(pa) measurements, with the mean volumes and maximum pressures of the left and right ventricles used to verify the accuracy of the fitted models. The inputs (GEDV, SV, P(ao), P(pa)) used in the identification process were matched by the CVS model to errors <0.5%. Prediction of the mean ventricular volumes and maximum ventricular pressures not used to fit the model compared experimental measurements to median absolute errors of 4.3% and 4.4%, which are equivalent to the measurement errors of currently used monitoring devices in the ICU (∼5-10%). These results validate the potential for implementing this approach in the intensive care unit.

Right ventricular failure complicating heart failure: pathophysiology, significance, and management strategies

Right heart failure most commonly results from the complication of left heart failure (systolic or nonsystolic dysfunction) or pulmonary hypertension. Over the past decade, greater attention has been paid to the role of right ventricular failure in the morbidity and mortality associated with cardiomyopathy and pulmonary hypertension. The right ventricle is distinct from the left ventricle not only in its spatial localization, but also in its response to increased afterload and signaling mechanisms. This article discusses the role of right ventricular failure in the setting of heart failure as well as the clinical diagnosis and management of right ventricular failure.

Effects of antiarrhythmic agents on left ventricular function during exercise in patients with chronic left ventricular dysfunction

This study was designed to determine the effects of antiarrhythmic agents on global left ventricular (LV) function during exercise in patients with chronic LV dysfunction. Thirty-five patients with LV dysfunction [LV ejection fraction (LVEF) < 45%] and ventricular arrhythmias were studied. They were randomly classified into 3 groups: patients who received a single oral dose of 6 mg/kg disopyramide phosphate (n = 12), those who received a single oral dose of 4 mg/kg mexiletine hydrochloride (n = 12), and those who received a single oral dose of 4 mg/kg pilsicainide hydrochloride (n = 11). First, all patients were subjected to baseline rest and peak exercise, equilibrium-gated cardiac-pool scintigraphy with 99mTc-human serous albumin of 740 MBq (baseline data). Second, on a separate day, they were given drugs once, and were subsequently subjected to rest and peak exercise equilibrium-gated cardiac-pool scintigraphy. Exercise LVEF and peak ejection rate (PER) after administration were significantly lower in the disopyramide and pilsicainide groups than in the mexiletine group (p < 0.05, respectively). The changes in LVEF and PER from rest to peak exercise after administration were significantly less than the baseline changes in those in the disopyramide and pilsicainide groups (p < 0.05, respectively). However, no significant changes in functional parameters were recognized in the mexiletine group. Due care should be taken when disopyramide and pilsicainide are administered to patients with chronic LV dysfunction since they reduce systolic LV function during exercise.

Use of ejection fraction (or lack thereof), morbidity/mortality and heart failure drug trials: a review

Ejection fraction (EF) is an ejection phase parameter used to assess the performance of the heart in normal individuals and pathologic states such as myocardial infarction, dilated cardiomyopathy, and congestive heart failure (CHF). It can be measured by radionuclide ventriculography, angiocardiography, echocardiography and magnetic resonance imaging. EF is dependent on the loading conditions of the heart as well as contractility of the myocardium which makes it a less useful measure of cardiac performance. Nevertheless, it has been widely utilized and discussed for years. EF has been used as an entry criteria for many trials in CHF and has been used to characterize the hemodynamic effects of various classes of drugs which are used in treating CHF. How predictive an increase in EF on therapy is of morbidity and mortality is a matter of debate. This review outlines the utilization (or lack thereof), of EF in various CHF drug trials, its relationship to symptomatic improvement and morbidity/mortality.

Effects of continuous positive airway pressure on cardiac volumes in patients with ischemic and dilated cardiomyopathy

The effects of continuous positive airway pressure (CPAP) on left (LV) and right ventricular (RV) volumes in patients with congestive heart failure (CHF) have not been studied. We hypothesized that CPAP would cause greater reductions in cardiac volumes in CHF patients with idiopathic dilated cardiomyopathy (IDC) than in those with ischemic cardiomyopathy (IsC), because their ventricles are more compliant. The effects of a 30-min CPAP application at 10 cm H(2)O on RV and LV end-diastolic (EDV) and end-systolic volumes (ESV), determined by radionuclide angiography, were therefore tested in 22 patients with CHF due to IsC (n = 13) or IDC (n = 9). CPAP-induced reductions in LVEDV, LVESV, RVEDV, and RVESV were significantly greater (p < 0.05) in the IDC than in the IsC group. Whereas in the IsC group CPAP caused no significant changes in LV or RV volumes, in the IDC group it induced significant reductions in RVEDV (527 +/- 77 ml to 354 +/- 50 ml, p = 0.03) and RVESV (400 +/- 78 ml to 272 +/- 54 ml, p = 0.04) that were greater than any reductions in LVEDV and LVESV. We conclude that CPAP causes greater short-term reductions in RV and LV volumes in CHF patients with IDC than in those with IsC, and that among patients with IDC, CPAP causes greater reductions in RV than in LV volumes.

The influence of diastolic and systolic function on exercise performance in heart failure due to dilated cardiomyopathy or ischemic heart disease

BACKGROUND

Peripheral adaptations and ventricular abnormalities influence physical performance in chronic heart failure. However, the role of the heart in determining exercise capacity has not been completely elucidated.

AIMS

To define cardiac determinants of exercise capacity in patients with dilated cardiomyopathy.

METHODS

In 101 patients with heart failure (NYHA class II-III) due to primary or ischemic dilated cardiomyopathy we measured peak exercise oxygen consumption (Pvo2), left ventricular ejection fraction (EF), left and right atrial and ventricular cavity dimensions, mitral and tricuspid flows. Patients were subdivided in class A (Pvo2 > 20 ml/min per kg; n = 44), class B (Pvo2 16-20 ml/min per kg; n = 42) and class C (Pvo2 < 16 ml/min per kg; n = 15).

RESULTS

Left ventricular diastolic and systolic dimensions, left atrial diameter, right atrial and ventricular areas were greater in class C than in class B and A; EF was lower in class C than in the other two classes; mitral peak flow velocity at early diastole (PFVE) and the ratio between early and late peak flow velocity (PFVE/PFVA) were higher in class C; mitral and tricuspid deceleration time (DT) in class B and A significantly exceeded those in class C. Peak vo2 was correlated with left and right ventricular dimensions, left atrial diameter, EF, mitral PFVE and PFVE/PFVA, mitral and tricuspid DT. Left ventricular EF, DT of the mitral valve and left ventricular diastolic diameter were independent predictors of peak vo2 at multivariate analysis.

CONCLUSIONS

In patients with dilated cardiomyopathy Pvo2 is related to left and right ventricular dimensions, left and right ventricular filling pattern and EF. Both systolic and diastolic dysfunction influence functional capacity.

Effects of inspiratory pressure support on oxygenation and central haemodynamics in the normal heart during the postoperative period

Ten patients without cardiac disease or pulmonary dysfunction were exposed to an inspiratory pressure of 0, 10 and 20 cmH2O, in random order, via a nasal mask during the first postoperative day after scoliotic surgery. These patients were in the supine position, and a BiPAP respiratory assist device was used. Arterial oxygen saturation increased significantly during the application of 10 and 20 cmH2O, while none of the haemodynamic parameters (cardiac output, central venous pressure, right ventricular ejection fraction, right ventricular end diastolic volume, mean pulmonary artery pressure, pulmonary artery wedge pressure, pulmonary vascular resistance) changed significantly, contrary to the findings during continuous positive airways pressure treatment. In addition, the BiPAP was generally well tolerated by the patients.

Cardiac output response to continuous positive airway pressure in congestive heart failure

The effects of nasal continuous positive airway pressure (CPAP) were examined during cardiac catheterization in 22 patients with congestive heart failure (CHF). CPAP was applied at a level of 5 cm H2O pressure. Hemodynamic measurements were made at baseline and while on CPAP. We hypothesized that patients with high left ventricular (LV) diastolic pressures would experience an increase in cardiac index (CI). To test this hypothesis, patients were divided into two groups based on their baseline pulmonary capillary wedge pressure (PCWP): one group of 11 whose PCWP was greater than or equal to 12 mm Hg (high-PCWP group) and a second group of 11 whose PCWP was less than 12 mm Hg (low-PCWP group). Among the high-PCWP group (mean PCWP +/- SEM = 19.0 +/- 2.7 mm Hg), CI rose significantly while on CPAP (from 2.48 +/- 0.26 to 2.82 +/- 0.26 L/min/m2, p less than 0.01). Stroke volume index (SVI) also rose significantly (from 52.6 +/- 7.0 to 64.1 +/- 8.0 ml/m2, p less than 0.001). In contrast, among the low-PCWP group (PCWP = 8.3 +/- 0.6 mm Hg), CI decreased significantly while on CPAP (from 3.14 +/- 0.44 to 2.89 +/- 0.62 ml/m2, p less than 0.025). SVI fell but not significantly while on CPAP (from 75.5 +/- 8.4 to 74.2 +/- 8.5 ml/m2). Multiple stepwise linear regression analysis revealed that the only significant correlate of the magnitude of change in CI in response to CPAP was baseline PCWP (r = 0.50, p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)