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

Blunted peripheral vasodilatory response is a hallmark of progressive deterioration in mild to moderate congestive heart failure

BACKGROUND

Several reports have shown that dilatory response to acetylcholine (ACh) and nitroprusside (SNP) is blunted in the limb vasculature in patients with congestive heart failure (CHF). However, it is not yet known whether this vascular dysfunction is related to clinical outcome. We have examined the relationship between peripheral vasodilatory response and prognosis of CHF.

METHODS AND RESULTS

A total of 46 patients with mild to moderate CHF were enrolled (mean age 56 years). Changes in forearm blood flow (FBF) during intra-arterial infusion of ACh and SNP were determined by plethysmography. FBF changes above baseline for each dose were cumulated and used as an index of endothelium-dependent (ACh) response and endothelium-independent (SNP) response, respectively. During the follow-up period (mean 32 months), 9 patients were admitted to the hospital for treatment of worsening refractory CHF, and 6 patients died suddenly or developed life-threatening arrhythmia. By Kaplan-Meier analysis, when all cardiac events were included, no significant differences were observed between any levels of vascular response in terms of prognosis. However, when deterioration events were analyzed separately, patients with SNP responses below the median (7.4 mL/min/dL) had significantly higher rates of hospital admission caused by worsening CHF than those with above the median responses (P <.05). This relationship was not found between ACh response and clinical outcome. By Cox multivariate analysis, blunted vasodilatory response to SNP was a significant predictor of worsening CHF (chi(2) = 3.95; P <.05).

CONCLUSION

This study has shown that patients with mild to moderate CHF showing a blunted vascular response to SNP rather than ACh were admitted to the hospital more frequently because of deterioration of CHF. This finding suggests that changes in vascular smooth muscle and/or vascular structure in the peripheral vasculature may be a critical element in the worsening of CHF.

Peripheral endothelial dysfunction in heart transplant recipients: possible role of proinflammatory cytokines

Endothelium-dependent vasodilation in the peripheral circulation may be impaired in heart transplant recipients (HTx rec). Conflicting results have been obtained and the mechanisms involved have not been examined. In the present study, we examined whether long-time survivors of heart transplantation (Tx) show signs of endothelial dysfunction in the peripheral microcirculation, and further investigated the possible role of endothelium-related markers and proinflammatory cytokines in this process. The vasodilatory responses to acetylcholine (Ach) (endothelium-dependent) and sodium nitroprusside (SNP) (endothelium-independent) were evaluated by skin laser-Doppler perfusion measurements in 63 clinically stable HTx rec 6 yr (range 1-13 yr) after Tx, and compared with 20 healthy controls. Ten HTx rec were also followed prospectively with three repeated measurements during the first year after Tx. Plasma von Willebrand factor, big-endothelin (b-ET), and proinflammatory cytokines were measured by enzyme immunoassays. Vascular responses to both Ach and SNP were significantly attenuated in the HTx rec compared with controls. In longitudinal testing, there was a significant reduction in endothelium-dependent vasodilation, but not independent vasodilation from 1 to 12 months after Tx. Plasma levels of vWF and b-ET, as well as levels of proinflammatory cytokines, tumor necrosis factor (TNF)-alpha, interleukin (IL)-6 and IL-1beta, were all markedly increased in HTx rec. HTx rec responses to Ach were negatively correlated to TNF-alpha levels in plasma (r = -0.39, p < 0.01). Moreover, there was also a significant positive correlation between plasma b-ET and TNF-alpha (r = 0.34, p < 0.01). In the long-term follow-up of HTx rec, endothelial dysfunction is demonstrated by both regulation of blood flow in the skin microcirculation and by raised markers of endothelial activation in plasma. This endothelial dysfunction may be related to enhanced levels of proinflammatory cytokines in these patients.

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.

Exercise skeletal muscle blood flow is related to peripheral microvascular stiffness in idiopathic dilated cardiomyopathy

Peripheral microvascular function plays an important role in congestive heart failure (CHF). Decreased exercise blood flow and microvascular dysfunction have been described in CHF and both factors are regarded as parameters that might influence exercise capacity in these patients. Whether these factors are related to or can be characterized in clinical severity of CHF has not been elucidated in this population. Skeletal muscle blood flow (SMBF) was measured continuously noninvasively, by means of the local isotope washout technique using (133)Xenon, in musculus tibialis anterior during graded maximal supine bicycle exercise. The distensibility in skeletal muscle was measured in a papaverine-relaxed vascular bed using (99m)Tc-pertechnetate. The investigation included 20 patients with moderate CHF (NYHA II), 11 patients with severe CHF (NYHA III, IV) due to idiopathic dilated cardiomyopathy (IDCM), and 31 age-matched healthy subjects. The maximal SMBF level was significantly lower in severe CHF (3.6 +/- 2.5 (ml x (100 g x min)(-1))) compared with moderate CHF (8.6 +/- 5.1 (ml x (100 g x min)(-1)); P < 0.005) and controls (11.0 +/- 4.1 (ml x (100 g x min)(-1)); P < 0.0001), but similar between moderate CHF and controls. Distensibility in skeletal muscle was decreased in severe CHF (12 +/- 8%) compared with controls (44 +/- 17%; P < 0.0001 vs severe CHF) and decreased with increasing severity of CHF (moderate CHF, 23 +/- 14%; P < 0.0005 vs controls). In CHF patients, a relationship was demonstrated between skeletal muscle distensibility and the maximal SMBF (P < 0.0001; r = 0.70). Moreover, maximal SMBF correlated directly to exercise time (P < 0.005; r = 0.54). Patients with CHF have reduced exercise SMBF, which may be a limiting factor for the reduced maximal exercise capacity. Moreover, microvascular distensibility in skeletal muscle is reduced and correlates to maximal exercise SMBF. Furthermore, maximal SMBF correlates to exercise time. This implies that increased skeletal muscle microvascular stiffness may contribute to the reduced blood flow during exercise and SMBF may partly limit exercise performance in CHF patients due to IDCM.

Exercise blod flow and microvascualr distensibility in skeletal muscle normalize after heart transplantation

This study investigated the effect of heart transplantation (HTX) on reduced exercise blood flow and microvascular stiffness in patients with congestive heart failure (CHF). Skeletal muscle blood flow (SMBF) during graded maximal supine bicycle exercise and microvascular distensibility (i.e., stiffness) were measured in musculus tibialis anterior by the isotope washout method. Measurements were performed in a cross-sectional study with 31 CHF patients and 28 patients, mean 9 months after HTX, and in a longitudinal study in 12 CHF patients before, 3 months, and 14 months after HTX, and in 31 healthy controls. Maximal SMBF: In the cross-sectional study, maximal SMBF was reduced in severe CHF patients (3.6 +/- 2.5 mL (100 g min)(-1)) and increased after HTX (7.7 +/- 4.8; p < 0.01 versus controls (11 +/- 4.1). Maximal SMBF was reduced in CHF patients (5.8 +/- 4.0) and reversed to normalization 3 months after HTX (10.3 +/- 4.4) in the longitudinal study. Microvascular distensibility: The distensibility was reduced (severe CHF, 12 +/- 8%; moderate CHF, 23 +/- 14%) in the cross-sectional study and increased after HTX towards normalization (38 +/-20%; controls: 44 +/- 17). In the longitudinal study, distensibility in CHF patients (14 +/- 6%) increased gradually to 32 +/- 12% (p < 0.005) at 3 months and normalized 14 months after HTX (46 +/- 17%). HTX gradually reversed the reduced SMBF and microvascular distensibility in CHF patients towards normalization.

Peripheral vascular remodeling in chronic heart failure: clinical relevance and new conceptualization of its mechanisms

Increased peripheral vascular tone is a critical factor in the deterioration of clinical stage and symptoms in chronic congestive heart failure (CHF) because of increased cardiac afterload and decreased nutritive skeletal muscle blood flow. Endothelial function as represented by nitric oxide (NO) production shows significant attenuation with the progression of clinical severity of CHF as determined by New York Heart Association class and exercise capacity parameters. This endothelial dysfunction emerges in the early stages of CHF. In the advanced stage of the condition, both endothelium-dependent and endothelium-independent dilator mechanisms are impaired in limb resistance vessels. This occurs because vascular endothelial function, especially NO production, is an important factor in the regulation of vasodilatory function, as well as making an important contribution to vascular structure. Furthermore, although such vasodilatory circulating factors as natriuretic polypeptides and newly discovered adrenomedullin are increased in heart failure, the vasodilatory potency of these polypeptide hormones in the limb vascular bed is significantly blunted. These observations suggest that peripheral circulatory failure in CHF is caused not only by simple arterial muscle constriction, but also by structural and functional changes, including receptor and postreceptor levels in the vasculature. This vascular remodeling may be an important mechanism underlying vasodilatory failure in both limb conduit and intraskeletal muscle vessels and may contribute significantly to left ventricular dysfunction and exercise intolerance in patients with heart failure.

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.

Exercise capacity in heart transplant recipients: relation to impaired endothelium-dependent vasodilation of the peripheral microcirculation

OBJECTIVES

The aim of this study was to examine the responses to endothelium-dependent and -independent vasodilators on the peripheral microcirculation in heart transplant recipients in relation to exercise capacity compared with that in healthy controls.

BACKGROUND

Impaired endothelium-dependent vasodilation of the microcirculation may play an important role in the limitation of exercise capacity after heart transplantation.

METHODS

Microvascular perfusion responses to four graded levels of iontophoretically applied 1% acetylcholine (endothelium-dependent vasodilator) and 1% sodium nitroprusside (SNP) (endothelium-independent) in the forearm skin of 42 transplant recipients and 16 age-matched controls were determined by laser Doppler perfusion measurements. Maximal exercise capacity was assessed by peak oxygen uptake (peak VO2) during progressive, symptom-limited, upright bicycle exercise.

RESULTS

With similar baseline perfusion levels in transplant recipients and controls (4.2 +/- 0.4 vs 4.6 +/- 0.6 arbitrary units [AU]), the increases in perfusion to acetylcholine, but not to SNP, were significantly attenuated in the transplant recipients: 7.0 +/- 1.0 vs 11.0 +/- 2.0, 12.7 +/- 1.5 vs 21.0 +/- 2.8, 21.0 +/- 1.9 vs 32.7 +/- 2.4, and 28.0 +/- 1.6 vs 39.2 +/- 2.4 AU, respectively (all p < 0.01). Peak VO2 was significantly lower in the transplant recipients (22.4 +/- 1.0 vs 38.0 +/- 2.9 ml/kg/min; p < 0.01). Furthermore, acetylcholine responses of the transplant recipients correlated closely to their peak VO2, irrespective of level of application (r = 0.63; p < 0.001, all four acetylcholine responses taken together), whereas no such correlation was found for SNP responses. In the control group, no relation was observed in acetylcholine/SNP responses to peak VO2.

CONCLUSIONS

Exercise limitation in transplant recipients appears strongly associated with attenuated endothelium-dependent vasodilation of the peripheral microcirculation.

Effect of heart transplantation on impaired peripheral microvascular perfusion and reactivity in congestive heart failure

Whether reduced peripheral blood flow in congestive heart failure is reversed after heart transplantation, has not been closely examined. We therefore studied skin microvascular resting perfusion and reactivity in patients pre- and postoperatively. Resting digital skin perfusion, together with the responses to cold pressor test, postocclusive reactive hyperemia and direct skin heating were examined with laser Doppler perfusion measurements. We examined 28 patients with congestive heart failure and 14 of these patients after heart transplantation and compared them to 13 healthy controls. Measurements were performed within 3 months preoperatively and 12 days, 1, 2, 3 and 6 months postoperatively. Patients with congestive heart failure had significantly lower resting perfusion levels than controls and demonstrated attenuated responses to both stimuli of vasodilation (all P<0.01). While peak hyperemic responses improved significantly after transplantation, postocclusive area under the hyperemic curve decreased further, and none of these variables were normalized after 6 months. In contrast, minimal perfusion during cold pressor test increased from a significantly lower level in the patients with congestive heart failure (P<0.05), to a level similar to that of the controls within 12 days postoperatively. Thus, skin microvascular perfusion and reactivity improve, but are not normalized within 6 months of transplantation. Both pre- and postoperative factors may be involved in maintaining a dysfunction of the peripheral microcirculation, which may contribute to exercise intolerance and hypertension in heart transplant recipients.