Increased plasma homocysteine concentrations accelerate cardiac allograft vasculopathy

Cardiac allograft vasculopathy: diagnosis, therapy, and prognosis

Development of cardiac allograft vasculopathy represents the major determinant of long-term survival in patients after heart transplantation. Due to graft denervation, these patients seldom present with classic symptoms of angina pectoris, and the first clinical presentations are progressive heart failure or sudden cardiac death. Although coronary angiography remains the routine technique for coronary artery disease detection, it is not sensitive enough for screening purposes. This is especially the case in the first year after transplantation when diffuse and concentric vascular changes can be easily detected only by intravascular ultrasound. The treatment of the established vasculopathy is disappointing, so the primary effort should be directed toward early prevention and diagnosis. Due to diffuse vascular changes, revascularization procedures are restricted only to a relatively small proportion of patients with favorable coronary anatomy. Percutaneous coronary intervention is preferred over surgical revascularization since it leads to better acute results and patient survival. Although there is no proven long-term advantage of drug-eluting stents for the treatment of in-stent restenosis, they are preferred over bare-metal stents. Severe vasculopathy has a poor prognosis and the only definitive treatment is retransplantation. This article reviews the present knowledge on the pathogenesis, diagnosis, treatment, and prognosis of cardiac allograft vasculopathy.

Homocysteine and P wave dispersion in patients with heart transplantation

BACKGROUND

Hyperhomocysteinemia (HHcy), a putative independent risk factor for the development of atherotrombosis in the general population, represents a very common finding in orthotopic heart transplantation (OHT) patients. Starting from previous studies suggesting a pro-arrhythmogenic activity of homocysteine (Hcy), we evaluated the possible correlation among Hcy plasma levels and P wave dispersion (PWD), corrected QT interval (QTc), and QTc dispersion (QTcD) as parameters of electric instability of the myocardium in patients undergone OHT whose hearts are therefore completely denervated, thus unresponsive to autonomic influences.

METHODS AND RESULTS

Homocysteine plasma levels, PWD, QTc, QTcD, and QTc dynamics were measured in 32 patients, who underwent OHT, and in 20 control subjects. In OHT patients, PWD (39.5 ± 11 vs. 34 ± 6 ms, p = 0.04) and QTc interval (438 ± 20 vs. 410 ± 10 ms, p < 0.001) were significantly higher in comparison with control subjects. Moreover, OHT subjects with HHcy had higher PWD values than those with normal Hcy plasma levels (44.1 ± 10.7 vs. 33.9 ± 8.8 ms, p = 0.007), but no difference was found between this latter OHT group and controls. Accordingly, in OHT patients, plasma Hcy level correlated significantly with PWD (Spearman r = 0.70; p < 0.0001), whereas no correlation was found with QTc, QTcD, and QTc circadian dynamics.

CONCLUSION

HHcy seems associated with an alteration in the electrical atrial conduction, possibly contributing, at least in part, to the increased risk of cardiac arrhythmias in the denervated hearts of OHT patients.

Long-term effect of folic acid therapy in heart transplant recipients: follow-up analysis of a randomized study

BACKGROUND

Folic acid therapy reduces homocysteine plasma levels, which seem to influence occurrence of cardiac allograft vasculopathy, but its effect on medium- or long-term prognosis after heart transplantation is unknown.

METHODS

We analyzed 7-year outcome of 51 recipients randomized to receive 15 mg/day of methyltertrahydrofolate for 1 year after heart transplantation or standard therapy alone (originally, for intravascular ultrasound study of short-term cardiac allograft vasculopathy progression); recipients were observed for a further 5 to 6 years.

RESULTS

Overall, 13 deaths occurred (six oncologic, five cardiovascular, two infective). Estimated 7-year survival was better in recipients randomized to folate (88%+/-6% vs. 61%+/-9%, P=0.04). After adjusting for age, pretransplant coronary artery disease, and hyperhomocysteinemia, posttransplant folic acid therapy was associated with lower mortality (relative risk [RR] 0.53, 95% confidence interval [CI] 0.25-0.97; P=0.036), apparently driven by reductions in both cancer-related and cardiovascular causes. Reduced mortality was marked in a high-risk subgroup comprising older recipients and patients transplanted because of coronary artery disease (RR 0.43, 95% CI 0.17-0.85) but not in the lower-risk subgroup (RR 1.11, 95% CI 0.22-5.61).

CONCLUSIONS

Although further studies are needed, it seems reasonable to suggest folate therapy to heart transplant recipients. It is possible that properties other than homocysteine reduction may provide antitumoral benefits.

Cardiac Allograft Vasculopathy: An Update

Allograft vasculopathy remains the nemesis of long-term survival in heart transplantation. Possible modifying risk factors such as obesity, diabetes, and hypertension should continue to be pursued aggressively. All patients should receive statins. Clinical trials will provide the evidence needed to ascertain whether mammalian target of rapamycin inhibitors should be used in de novo cardiac transplant recipients to attenuate cardiac allograft vasculopathy (CAV). Intravascular ultrasound appears to play a key role in the diagnosis and evaluation of new treatments, and may indeed represent a surrogate marker that can be used to tailor management and improve outcomes. A better understanding of CAV is needed to develop targeted preventive therapies. Ongoing research in native atherosclerosis and vascular biology may provide answers within the next decade.

Subclinical Inflammation and Prothrombotic State in Heart Transplant Recipients: Impact of Cyclosporin Microemulsion vs. Tacrolimus

BACKGROUND

Subclinical inflammation is related to adverse events in patients with coronary artery disease. In the present study, we determined the changes in hemostatic parameters and inflammatory markers in a large cohort of dyslipidemic cardiac transplant recipients compared with dyslipidemic healthy controls, and the effect of cyclosporin microemulsion (CsA) vs. tacrolimus immunoprophylaxis on these parameters.

METHODS

Stable cardiac transplant recipients (n=129) aged 56.7+/-10.1 years, 79+/-42 months postcardiac transplantation, and 26 mildly dyslipidemic healthy control subjects had serum measurements for lipids and lipoproteins, hemostatic parameters, and selected inflammatory markers. Transplant recipients were randomized to either continuation of CsA maintenance or conversion to tacrolimus immunoprophylaxis and were reassessed after six months.

RESULTS

CsA-maintained cardiac transplant recipients exhibited a significant elevation in Factor VIII, Von Willebrand factor, fibrinogen and PAI-I compared with healthy control subjects (all P<0.05). Similarly, cardiac transplant patients yielded a significantly elevated C-reactive protein (CRP) (4.11+/-6.25 [transplant group (TX)] vs. 2.09+/-2.21 mg/L [control group (CTL)]; P=0.0195), and homocysteine (19.2+/-8.8 [TX] vs. 9.70+/-2.45 microM [CTL]; P<0.001). VCAM, ICAM, E- and P-selectins were also significantly higher in transplant patients than in controls (all P<0.05). The conversion from CsA to tacrolimus resulted in a significant decrease in uric acid, total- and LDL-cholesterol, apolipoprotein B, creatinine, and homocysteine levels (all P<0.05).

CONCLUSIONS

Stable long-term CsA-maintained cardiac transplant patients exhibit a significant and general increase in hemostatic parameters and markers for subclinical inflammation. Tacrolimus conversion improved the patient lipid profile and decreased serum creatinine, uric acid, and homocysteine without any significant effect on the other markers.

Contemporary concepts in prevention and treatment of cardiac allograft vasculopathy

Cardiac allograft vasculopathy (CAV), is characterized by heterogeneous proliferative thickening of the vascular intima of the cardiac allograft vasculature. Since its presentation is commonly clinically silent, early diagnosis and preventative therapy are critical. Preventative therapy including optimization of immunosuppressive therapy and treatment of comorbidities associated with CAV progression must be initiated early since most of the intimal thickening occurs during the first year posttransplant. Long-term use of calcineurin inhibitors is associated with a high incidence of chronic renal disease and also contributes to hyperlipidemia and hypertension, all of which may exacerbate CAV. In addition, statins, antihypertensive agents and anti-CMV agents all have demonstrated benefits in reducing CAV. Once established, the limited treatment options include nonpharmacologic interventions such as retransplantation, percutaneous coronary interventions, coronary artery bypass grafting, transmyocardial laser revascularization and heparin-induced/mediated extracorporeal LDL plasmapheresis (HELP). As the use of new assessment tools increases our understanding of this disease, better preventative and treatment strategies are evolving.

Cardiac allograft vasculopathy in pediatric heart transplant recipients

Metabolic parameters for coronary allograft vasculopathy (CAV) have not been well defined in children. CAV (by angiography or autopsy) was studied in 337 heart recipients on a cyclosporine-based steroid-sparing regimen. Freedom from CAV for all was 79% at 10 years. Fifty-nine patients (18%) developed CAV at a mean of 6.5 +/- 3 years post-transplant. First year rejections were significantly higher in CAV, mean 2.3 vs. 1.4, P = 0.003, odds ratio (OR) 1.8. Rejection with hemodynamic compromise beyond 1 year post-transplant was associated with CAV, P < 0.001, OR 8.4. There was no significant correlation among human leukocyte antigen DR (HLA DR) mismatch, pacemaker use or homocysteine levels and the development of CAV. Maximum cholesterol and low density lipoprotein (LDL) levels were not significantly different. Neither diabetes nor hypertension was significant predictors of CAV on multivariate logistic regression analysis. In conclusion, frequent and severe rejection episodes may predict pediatric CAV. Neither glucose intolerance nor lipid abnormalities appeared to alter risk for CAV in this population.