Insights into ventricular repolarization abnormalities in 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.

Statin-associated QTc Interval Shortening as Prognostic Indicator in Heart Transplant Recipients

Statin treatment promotes survival after cardiac transplantation by reducing cholesterol levels, allograft rejection, and transplant coronary artery disease. Analysis of data from 114 heart transplant recipients (including 86 treated with statins for < or =1 year post-transplantation) revealed that statins were associated with shortened corrected QT intervals (QTc), reduced low-density lipoprotein cholesterol, and reduced transplant coronary artery disease incidence at 1 year and improved survival at 5 years. Statin-associated QTc shortening thus appears to be a favorable prognostic sign after transplantation.

ECG manifestations: noncoronary heart disease

The electrocardiogram reflects changes to the heart beyond those seen in acute myocardial infarction and acute coronary syndromes. Diseases of the pericardium and heart muscle such as pericarditis,myocarditis, and pericardial effusion have characteristic manifestations. Hypertensive heart disease is associated with a variety of changes on the electrocardiogram, as is valvular heart disease. Cardiac rhythm disturbances have been associated with the Brugada syndrome and the long QT syndrome, both of which have telltale findings on the electrocardiogram. The manifestations of dextrocardia, although rare, should be familiar to those who interpret electro-cardiograms. Transplanted hearts also feature classic changes, both in health and in stages of rejection. The various electrocardiographic manifestations of these noncoronary heart diseases are reviewed here.

Surface electrocardiography and histologic rejection following orthotopic heart transplantation

BACKGROUND

Intraventricular conduction delay and QT interval dispersion may be related to electrical instability and the risk of ventricular arrhythmogenesis. The interlead variability of the QT interval on a surface 12-lead electrocardiogram (ECG) has been associated with an increased likelihood of sudden death in patients with long QT syndromes, in patients recovering from myocardial infarction, and dilated cardiomyopathy. We sought to determine the incidence of increased QT(c) dispersion (QT(c-d)) relative to biopsy grade of severity of rejection.

METHODS

Records of patients having undergone orthotopic heart transplantation (OHT) were reviewed focusing specifically on surface ECGs performed in temporal proximity to endomyocardial biopsy.

RESULTS

Seventy-five patients were evaluated on 1573 occasions, to include 999 surface ECGs, and 847 endomyocardial biopsies. There were 269 interpretable surface ECGs and endomyocardial biopsies performed within 1.1 +/- 4.6 days. There were no identifiable trends in atrioventricular or intraventricular conduction abnormalities (to include right bundle branch block) when comparing those with and without significant rejection on endomyocardial biopsy. The mean QT(c-d) of those with none (n = 34), mild (n = 194), moderate (n = 39), and severe (n = 2) rejection was 49 +/- 29, 49 +/- 35, 57 +/- 38, 81 +/- 7 ms, respectively (P = 0.28 by ANOVA of means). When comparing those with significant rejection so as to change management there was a trend toward increased dispersion (no to mild rejection, 49 +/- 34 ms vs moderate to severe rejection, 59 +/- 37 ms, P = 0.09).

CONCLUSIONS

In this study investigating noninvasive ventricular depolarization/repolarization and correlation to histologic manifestation of rejection, there was suggestion, but no statistical significance, of QT(c-d) and severity of rejection. QT(c-d) should not be considered a sensitive marker for OHT rejection.

Relation of QTc duration heterogeneity to mortality following orthotopic heart transplantation

Studies of heart failure patients have demonstrated that serial QT prolongation and abnormally prolonged QT intervals are associated with greater mortality. Serial QT interval measurements in patients who undergo orthotopic heart transplantation (OHT) may quantify the degree of myocardial repolarization heterogeneity and serve as a marker of arrhythmogenic substrate. In this study, the mean survival for those with "stable" QT(c) intervals (a change of -10 to 10 ms/year) was 124 +/- 8 months versus 63 +/- 25 months in those with annual QT(c) changes of >10 ms (p = 0.009). Ventricular repolarization heterogeneity may serve as a marker of identifying high-risk patients after OHT.

Anything but a biopsy: noninvasive monitoring for cardiac allograft rejection

Endomyocardial biopsy has stood the test of time as a surveillance technique; however, the expense, resources required, invasive nature, and low but definite risks have motivated investigators to pursue less invasive techniques. The search for noninvasive surveillance techniques for cardiac rejection have centered on measurements of cardiac function, intragraft electrical events, peripheral proteomic markers of graft micronecrosis, immune activation, and nonimmune accompaniments of rejection. Although several investigations allude to a reasonable negative predictive value of such monitoring, the specificity of these techniques remains poor. Until well-constructed studies not only define the predictive values of noninvasive techniques but also appropriately evaluate the clinical safety of any such approach, invasive endomyocardial biopsy will remain the gold standard.