Abnormal baroreceptor-mediated vasodilation of the peripheral circulation in congestive heart failure secondary to idiopathic dilated cardiomyopathy

Cardiopulmonary Exercise Testing as a Tool for Diagnosing Pulmonary Hypertension in Patients with Dilated Cardiomyopathy

Background

Recently, it has become increasingly recognized that pulmonary hypertension (PH) is a particularly threatening result of left‐sided heart disease. However, there have been few investigations of the impact of cardiopulmonary exercise testing (CPX) variables on PH in dilated cardiomyopathy (DCM). We evaluated the usefulness of crucial CPX variables for detecting elevated pulmonary arterial pressure (PAP) in patients with DCM.

Methods

Ninety subjects with DCM underwent cardiac catheterization and CPX at our hospital. Receiver operator characteristic (ROC) analysis was performed to assess the ability of CPX variables to distinguish between the presence and absence of PH.

Results

Overall mean values were: mean PAP (mPAP), 18.0 ± 9.6 mmHg; plasma brain natriuretic peptide, 233 ± 295 pg/mL; and left ventricular ejection fraction, 30.2 ± 11.0%. Patients were allocated to one of two groups on the basis of mean PAP, namely DCM without PH [mean PAP (mPAP) <25 mmHg; n = 75] and DCM with PH (mPAP ≥25 mmHg; n = 15). A cutoff achieved percentage of predicted peak VO₂ (%PPeak VO₂) of 52.5% was the best predictor of an mPAP ≥25 mmHg in the ROC analysis (area under curve: 0.911). In the multivariate analysis, %PPeak VO₂ was the only significant independent predictor of PH (Wald 6.52, odds ratio 0.892, 95% CI 0.818–0.974; P = 0.011).

Conclusions

%PPeak VO₂ was strongly associated with the presence of PH in patients with DCM. Taken together, these findings indicate that CPX variables could be important for diagnosing PH in patients with DCM.

A cardiovascular mathematical model of graded head-up tilt

A lumped parameter model of the cardiovascular system has been developed and optimized using experimental data obtained from 13 healthy subjects during graded head-up tilt (HUT) from the supine position to . The model includes descriptions of the left and right heart, direct ventricular interaction through the septum and pericardium, the systemic and pulmonary circulations, nonlinear pressure volume relationship of the lower body compartment, arterial and cardiopulmonary baroreceptors, as well as autoregulatory mechanisms. A number of important features, including the separate effects of arterial and cardiopulmonary baroreflexes, and autoregulation in the lower body, as well as diastolic ventricular interaction through the pericardium have been included and tested for their significance. Furthermore, the individual effect of parameter associated with heart failure, including LV and RV contractility, baseline systemic vascular resistance, pulmonary vascular resistance, total blood volume, LV diastolic stiffness and reflex gain on HUT response have also been investigated. Our fitted model compares favorably with our experimental measurements and published literature at a range of tilt angles, in terms of both global and regional hemodynamic variables. Compared to the normal condition, a simulated congestive heart failure condition produced a blunted response to HUT with regards to the percentage changes in cardiac output, stroke volume, end diastolic volume and effector response (i.e., heart contractility, venous unstressed volume, systemic vascular resistance and heart rate) with progressive tilting.

Association between cardiopulmonary exercise and dobutamine stress testing in ambulatory patients with idiopathic dilated cardiomyopathy: a comparison with peak VO₂ and VE/VCO₂ slope

BACKGROUND

Both peak VO(2) and VE/VCO(2) slope are considered to be useful predictors of cardiovascular events. The left ventricular (LV) response to dobutamine stress testing (DST) also provides useful prognostic information. However, the relationship between these variables has not been fully investigated. Therefore, the aim of this study is to investigate the association between myocardial contractile reserve measured by DST and cardiopulmonary exercise testing (CPX) variables in patients with idiopathic dilated cardiomyopathy (IDCM).

METHODS

Thirty-eight patients were subjected to CPX as well as cardiac catheterization for measurement of LV pressure. The maximum first derivative of LV pressure (LV dP/dt(max)) was measured at baseline and during dobutamine infusion at incremental doses of 5, 10, and 15 μg kg(-1)min(-1). LV dP/dt(max) at baseline and the percentage increase in LV dP/dt(max) (ΔLV dP/dt(max)) induced by DST served as indices of LV contractility and myocardial contractile reserve, respectively.

RESULTS

Peak VO(2), and VE/VCO(2) slope were 18.6 mL kg(-1)min(-1) and 32.3, respectively. Peak VO(2) was not correlated with LV dP/dt(max) at baseline. However, peak VO(2) was significantly correlated with ΔLV dP/dt(max), and the correlation became more pronounced as the dose of dobutamine was increased. There was no correlation between VE/VCO(2) slope and ΔLV dP/dt(max). Multivariate regression analysis revealed that ΔLV dP/dt(max) was independently correlated with peak VO(2) (p=0.011).

CONCLUSIONS

Peak VO(2), but not VE/VCO(2) slope, may reflect myocardial contractile reserve in ambulatory patients with IDCM. This study population is small, and therefore large confirmatory studies are needed.

Recurrent orthostatic syncope due to left atrial and left ventricular collapse after a continuous-flow left ventricular assist device implantation

Left ventricular assist devices (LVADs) have become an established treatment for patients with advanced heart failure as a bridge to transplantation or for permanent support as an alternative to heart transplantation. Continuous-flow LVADs have been shown to improve outcomes, including survival, and reduce device failure compared with pulsatile devices. Although LVADs have been shown to be a good option for patients with end-stage heart failure, unanticipated complications may occur. We describe dynamic left atrial and left ventricular chamber collapse related to postural changes in a patient with a recent continuous-flow LVAD implantation.

Static magnetic field effect on the arterial baroreflex-mediated control of microcirculation: implications for cardiovascular effects due to environmental magnetic fields

Increasing evidence suggests that time-varying and static magnetic fields in the environment might affect the cardiovascular system. To explore the underlying physiology, the effect of static magnetic fields (SMFs) on the carotid baroreflex control of microcirculation was studied. Twenty-four hemodynamic monitorings were performed in rabbits sedated by pentobarbital infusion (5 mg/kg/h) during experiments that lasted 120 min. Mean femoral artery blood pressure, heart rate, and ear lobe skin microcirculatory blood flow, measured by microphotoelectric plethysmogram (MPPG), were simultaneously recorded before and after a 40 min exposure of the sinocarotid baroreceptors to Nd(2)-Fe(14)-B alloy magnets (n = 14) or sham magnets (n = 10, control series). The local SMF field was 350 mT, at the baroreceptors' site. Arterial baroreflex sensitivity (BRS) was estimated from heart rate/blood pressure response to intravenous bolus injections of nitroprusside and phenylephrine. A significant positive correlation was found between the SMF-induced increase in BRS (DeltaBRS = BRS(afterSMF) - BRS(priorSMF)) and the increment in microvascular blood flow (DeltaMPPG = MPPG(afterSMF) - MPPG(priorSMF)) (r = 0.66, p < 0.009). The SMF probably modulated the arterial baroreflex-mediated microcirculatory control. This could represent one possible mechanism how environmental magnetic fields act on the cardiovascular system, and a method how to complexly adjust macro- and microcirculation with potential clinical implementation.

Neurocardiogenic mechanisms of unexplained syncope in idiopathic dilated cardiomyopathy

Syncope in patients with advanced heart failure is a sign of poor prognosis. The cause of syncope in patients with dilated cardiomyopathy (DC) is not fully recognized and may remain elusive even after standardized evaluation. The purpose of the present study was to examine the implication of neurally mediated mechanisms in the pathophysiology of syncopal episodes in patients with DC. Twenty-six patients (21 men, 5 women; mean age 59 +/- 2 years, range 38 to 79) with DC and left ventricular ejection fractions <or=40% were included in the study. Thirteen patients with unexplained syncope or presyncope and a control group of 13 patients without unexplained syncope underwent head-up tilt tests with clomipramine challenge. The 2 groups were matched with regard to age, gender, and left ventricular ejection fractions, and there were no major differences in terms of medication. Heart rate variability analysis and plethysmography of forearm flow were performed during the tilt tests. Blood samples were also drawn for catecholamine measurements. In the group with histories of unexplained syncope, the head-up tilt test results were positive in 11 patients (84.6%). Sympathetic and parasympathetic heart rate indexes were markedly stimulated, while catecholamine concentrations and blood flow changes indicated sympathetic withdrawal during tilting. In the control group, the head-up tilt test results were negative in 12 patients (92.3%). In conclusion, neurally mediated mechanisms seem to be implicated in the pathophysiology of syncope in patients with DC and should therefore be considered in the differential diagnosis of syncopal episodes of unexplained origin.

Olprinone: a phosphodiesterase III inhibitor with positive inotropic and vasodilator effects

Olprinone is a newly developed phosphodiesterase III inhibitor characterized by several properties. First, olprinone has positive inotropic and vasodilator actions and improves myocardial mechanical efficiency. Second, olprinone augments cerebral blood flow by a direct vasodilatory effect on cerebral arteries. The cerebrovascular reactivity to olprinone is marked in patients with impaired cerebral circulation. Third, olprinone selectively improves carotid artery distensibility, which may be attributable to differences in the arterial structural components or the reactivity of smooth muscle cells to olprinone. Fourth, olprinone improves inadequate redistribution of brain perfusion and may prevent cerebral metabolic abnormalities in heart failure.

Cardiovascular and neuroendocrine responses to water immersion in compensated heart failure

The hypothesis was tested that cardiovascular and neuroendocrine (norepinephrine, renin, and vasopressin) responses to central blood volume expansion are blunted in compensated heart failure (HF). Nine HF patients [New York Heart Association class II-III, ejection fraction = 0.28 +/- 0.02 (SE)] and 10 age-matched controls (ejection fraction = 0.68 +/- 0.03) underwent 30 min of thermoneutral (34.7 +/- 0.02 degrees C) water immersion (WI) to the xiphoid process. WI increased (P < 0.05) central venous pressure by 3.7 +/- 0.6 and 3.2 +/- 0.4 mmHg and stroke volume index by 12.2 +/- 2.1 and 7.2 +/- 2.1 ml. beat(-1). m(-2) in controls and HF patients, respectively. During WI, systemic vascular resistance decreased (P < 0.05) similarly by 365 +/- 66 and 582 +/- 227 dyn. s. cm(-5) in controls and HF patients, respectively. Forearm subcutaneous vascular resistance decreased by 19 +/- 7% (P < 0.05) in controls but did not change in HF patients. Heart rate decreased less during WI in HF patients, whereas release of norepinephrine, renin, and vasopressin was suppressed similarly in the two groups. We suggest that reflex control of forearm vascular beds and heart rate is blunted in compensated HF but that baroreflex-mediated systemic vasodilatation and neuroendocrine responses to central blood volume expansion are preserved.

Calf blood flow during prolonged tilt in idiopathic dilated cardiomyopathy and after cardiac transplantation

In severe congestive heart failure (CHF), abnormal reflex control of calf blood flow during brief head-up tilt that appears to normalize after transplantation (HTX) may be present during prolonged observation also. Therefore, we studied the effect of prolonged (30 min) 50 degrees head-up tilt on calf skeletal muscle blood flow measured by the local (133)Xe washout method in CHF and after HTX and in patients with the presence vs. absence of native right atrium (+PNA and -PNA, respectively). During brief head-up tilt, skeletal muscle blood flow increased 13 +/- 42% in 9 severe CHF patients in contrast to a -28 +/- 22% decrease (P < 0.01) in 11 control subjects, -24 +/- 30% decrease in 15 moderate CHF patients (P < 0.05), -25 +/- 14% decrease in 12 patients with recent HTX (P < 0.01), and -21 +/- 24% decrease in 8 patients with distant HTX (P = 0.06). However, during sustained tilt, blood flow declined to similar levels of that in the other groups in severe CHF. HTX -PNA vs. +PNA showed blunted skeletal muscle vasomotor control (P < 0.05) and a higher systolic blood pressure (139 +/- 14 vs. 125 +/- 15 mmHg, P < 0.05) and heart rate (92 +/- 10 vs. 83 +/- 8 beats/min, P < 0.05). Thus paradox vasodilatation of calf skeletal muscle in severe CHF is present only during brief but not prolonged tilt. This may be one explanation of the rare presence of orthostatic intolerance in CHF and implies only a minor possible role for the abnormality in edema pathogenesis. Removal of all right atrium in HTX has an important hemodynamic impact that may possibly affect later clinical outcome.

Effects of passive tilting on capillary filtration in the lower leg in idiopathic dilated cardiomyopathy and after heart transplantation for the same condition

Abnormal reflex control of the peripheral microvasculature during orthostasis in congestive heart failure (CHF) and after heart transplantation (HT) may cause failure of microvascular homeostasis and peripheral edema. We explored the effect of passive head-up tilt on lower leg capillary filtration measured by strain-gauge plethysmography in 24 patients with CHF, in 20 patients after HT (12 patients with preserved native right atrium, 8 patients without native right atrium), and in 18 controls. We hypothesized that an impaired peripheral microvascular reflex during orthostasis in CHF and HT might allow increased arterial hydrostatic pressure to increase pressure at the capillary level. To identify an impact of changes in arterial hydrostatic pressure, capillary fluid filtration was expressed per mm Hg arterial hydrostatic pressure (capillary filtration coefficient(arterial pressure) [CFC(AP)]) and was measured (1) during elevated venous pressure alone (50 mm Hg venous stasis in supine position), and (2) during elevated hydrostatic pressure at both the venous and arterial side of the vascular tree (head-up tilt with a vertical distance from the right atrium to the strain-gauge of 68 cm of water [50 mmHg]). Elevated venous pressure alone resulted in the highest CFC(AP) in controls (0.79+/-0.28 ml/min x 100 ml mm Hg x 10(-3)+/-SD) versus those with CHF (0.44+/-0.23, p <0.0001) and those after HT (0.54+/-0.22, p <0.01). However, during head-up tilt, CFC(AP) was similar in all 3 groups, because CFC(AP) decreased in controls (to 0.49+/-0.22, p <0.0001), in contrast to unchanged CFC(AP) in those with CHF (0.43+/-0.24) and in those with HT (0.50+/-0.21). HT patients with complete removal of the native right atrium had higher CFC(AP) (0.62+/-0.17) during head-up tilt than patients with preserved native right atrium (0.36+/-0.16, p <0.005). In conclusion, patients with CHF and those after HT have increased capillary filtration to a lesser degree than controls during elevated venous pressure alone. However, during orthostasis this apparent edema-protective mechanism vanishes, probably because of compromised microvascular reflex control. During daily upright activities, this may be one important factor in the edema pathogenesis. The phenomenon is particularly distinct in HT patients without preserved native right atrium.

Regional blood flow in the calf and plasma endothelin during prolonged orthostasis in humans

This study tested the hypothesis that circulating plasma levels of the vasoconstrictor endothelin increase during prolonged orthostasis in association with changes in both calf regional blood flow, systemic arterial blood pressure and heart rate, and that the 133Xenon wash-out method can be used for prolonged registration of skeletal muscle blood flow. The simultaneous effects of prolonged orthostasis on plasma endothelin, calf skeletal muscle and subcutaneous blood flow, heart rate and arterial blood pressure were investigated in 13 healthy subjects before, during and after 30 min of 50 degree head-up tilt. Blood flow rate was measured by the local 133Xenon wash-out method in the supine position and during 50 degree head-up tilt. The method was evaluated for skeletal muscle for prolonged observation in the supine position in five subjects and compared with blood flow rates measured with plethysmography. Plasma endothelin was unchanged during head-up tilt, despite a maximal reduction in skeletal muscle blood flow rate of 47% (p<0.001) and subcutaneous blood flow rate of 80% (p<0.01) and a maximal increase in heart rate of 15% (p<0.001) and diastolic (12%, p<0.01) blood pressure. The skeletal muscle wash-out curves for 133Xenon were monoexponential from 30 min after injection and at least during the next hour and correlated with total limb blood flow rate assessed simultaneously with plethysmography (r=0.76, p<0.0001). Circulating endothelin does not appear to be in the first line of regulation of calf microcirculation, systemic arterial blood pressure or heart rate during prolonged orthostasis. The 133Xenon wash-out method can be used for prolonged measurement of skeletal muscle blood flow.

Reversal of peripheral microvascular dysfunction during long-term treatment with the angiotensin-converting enzyme inhibitor fosinopril in congestive heart failure

BACKGROUND

Treatment with angiotensin-converting enzyme (ACE) inhibitors in congestive heart failure (CHF) improves cardiac and peripheral hemodynamic function and exercise performance. However, studies on the effects of long-term treatment with an ACE inhibitor on the neurogenic and nonneurogenic regulation and structural microangiopathy of the peripheral microvasculature in CHF are lacking.

METHODS AND RESULTS

We investigated the effect of 12 weeks of treatment with the ACE inhibitor fosinopril on peripheral microvascular function in a double-blind, placebo-controlled study of 12 patients treated with fosinopril and 10 patients treated with placebo. All had moderate CHF. Microvascular blood flow and resistance were calculated after application of the local isotope washout method in relaxed and nonrelaxed calf vascular beds in the supine position and during head-up tilt. Skeletal muscle vascular resistance was reduced in the fosinopril group (46 +/- 6 to 30 +/- 1 mm Hg.mL-1.100 g.min +/- standard error; P < .05) and differed compared with the effect of placebo (P < .05) where no change was seen (37 +/- 11 to 55 +/- 13 mm Hg.mL-1.100 g.min; not significant [NS]). Also, skin minimal vascular resistance was reduced during fosinopril treatment (13 +/- 0.6 to 11 +/- 0.7 mm Hg.mL-1.100 g.min; P < .05) and differed compared with the effect of placebo (P < .05) with absence of change (12 +/- 1.6 to 14 +/- 1.4 mm Hg.mL-1.100 g.min; NS).

CONCLUSIONS

These results suggest that long-term ACE inhibitor treatment with fosinopril in patients with CHF improves hemodynamic status to as far as the peripheral microvascular level in both the relaxed and nonrelaxed microcirculation of the lower leg.

Skin microvascular distensibility and structural microangiopathy in idiopathic dilated cardiomyopathy and after heart transplantation

Peripheral microvascular function plays an important role in patients with congestive heart failure (CHF). Decreased microvascular distensibility in skin and structural microangiopathy of the lower leg have been demonstrated in CHF due to idiopathic dilated cardiomyopathy. Whether microvascular skin distensibility reverses after heart transplantation and is related to the structural microangiopathy has not been elucidated before now. Distensibility (stiffness) of resistance vessels in the skin was measured using the local isotope washout method in a histamine-relaxed vascular bed at the dorsum of the foot. The structure of terminal arterioles was determined from skin biopsies. The measurements were performed in two studies. A cross-sectional study included 20 patients with clinical moderate CHF (NYHA II), 11 severe CHF patients (NYHA III and IV), and 28 patients 9 +/- 6 months (mean +/- SD) after heart transplantation (HTX). Furthermore, 12 patients were studied in a longitudinal study before (CHF) and 3 +/- 1 months (HTX-3) and 14 +/- 4 months (HTX-14) after HTX. A control group of 24 healthy subjects was included. In the cross-sectional study, distensibility in skin was reduced with increasing severity of CHF (severe CHF 22 +/- 10% and moderate CHF 38 +/- 21% vs controls 54 +/- 14%; P < 0.0001 and P < 0.01, respectively). Distensibility was reduced in patients after HTX (HTX, 41 +/- 18%) compared to controls (P < 0.01). In the longitudinal study, distensibility was decreased before transplantation (20 +/- 10%, P < 0.0001 vs controls) and increased gradually after HTX to 35 +/- 16% at 3 months (P < 0.01 vs CHF, P < 0.005 vs controls) and to 40 +/- 12% at 14 months (P < 0.05 vs controls, P < 0.01 vs HTX-3, P < 0.005 vs CHF). Structural microangiopathy was demonstrated in CHF, but not in HTX, in the cross-sectional study. However, a normalization could not be demonstrated after HTX in the longitudinal study. We conclude that the decreased microvascular skin distensibility (increased stiffness) gradually reverses after HTX. Furthermore, the structural microangiopathy seems to improve gradually.

Plasma endothelin in congestive heart failure: a predictor of cardiac death?

BACKGROUND

Endothelin is a potent vasoconstrictor, with growth-promoting and possible cardiotoxic and arrhythmogenic properties. This study investigates the association between increased plasma endothelin in congestive heart failure and prognosis.

METHODS AND RESULTS

Forty-four patients with congestive heart failure showed increased plasma endothelin concentrations (mean +/- SD, 3.7 +/- 1.7 pg/mL; n = 44) compared with healthy volunteers (2.0 +/- 0.4 pg/mL, n = 21, P < .00003). Plasma endothelin increased with the severity of the disease. All patients were followed for an average of 17 months (range, 2-25 months). Cardiac mortality was 27% (8 of 30 patients) in the group with plasma endothelin concentrations above 3 pg/mL and 0% (0 of 14 patients) in the group with plasma endothelin concentrations below 3 pg/mL (P < .05). In contrast, separation of patients based on different New York Heart Association groups and ejection fractions revealed no significant difference regarding this endpoint.

CONCLUSIONS

Increased plasma endothelin concentrations in patients with congestive heart failure appears to serve as a predictor of cardiac death.

Effects of orthotopic cardiac transplantation on structural microangiopathy and abnormal hemodynamics in idiopathic dilated cardiomyopathy

To examine whether cardiac transplantation would reverse morphologic and hemodynamic changes in peripheral circulation in idiopathic dilated cardiomyopathy, the structure of terminal arterioles and minimal vascular resistance were measured in skin at the dorsum of the foot in the same 14 patients before and 80 +/- 21 (mean +/- SD) days and 387 +/- 46 days after transplantation. The results were compared with data from a group of 16 healthy subjects. Blood flow was measured by the local technetium-99m pertechnetate washout method in a vascular bed relaxed with histamine. Structural microangiopathy (enhanced thickening of the basement membranes) in the arterioles was disclosed in skin biopsies in 11 of 14 patients before transplant, but in none of the 16 control subjects (p < 0.002). These abnormalities were unchanged 80 days after cardiac transplantation. However, arteriolar wall thickening was significantly reduced over the 1-year period after transplantation (p < 0.05), but this was not complete. Transplantation also led to a significant delayed decrease in minimal vascular resistance: before transplantation, 10.1 +/- 3.2 mm Hg.ml-1.100 g.min (mean +/- SD); 80 days after transplantation, 9.3 +/- 3.1 mm Hg.ml-1.100 g.min (p = NS), and 1 year after transplantation 7.6 +/- 2.4 mm Hg.ml-1 100 g.min (p < 0.01). Minimal vascular resistance before and 80 days after transplantation was significantly increased compared with that in healthy control subjects (6.3 +/- 1.7 mm Hg.ml-1 100g.min [p < 0.0003 and p < 0.003, respectively]). However, 1 year after transplantation, minimal vascular resistance was reduced to comparable levels when compared with that in control subjects (p = NS). These results indicate that structural microangiopathy and minimal vascular resistance in skin are improved slowly and gradually within the first year after orthotopic cardiac transplantation in patients with idiopathic dilated cardiomyopathy, however, the remodeling of histopathology is not accompanied by complete normalization.