Biological correlates of QT interval and QT dispersion in 2,265 patients with left ventricular ejection fraction < or =40%

Parathyroid hormone is related to QT interval independent of serum calcium in patients with coronary artery disease

BACKGROUND

Elevated serum parathyroid hormone (PTH) is associated with increased risk of cardiovascular death, including sudden cardiac death, in patients with and without parathyroid disease. In small studies, PTH levels have been associated with changes in cardiac conduction and repolarization. Changes in the corrected QT interval (QTc) in particular are thought to be mediated by the effect of PTH on serum calcium. There is limited evidence to suggest PTH may affect cardiac physiology independent of its effects on serum calcium, but there is even less data linking PTH to changes in electrical conduction and repolarization independent of serum calcium.

METHODS

ECG data were examined from the PULSE database-an observational cohort study designed to examine depression after acute coronary syndromes (ACS) at a single, urban American medical center. In all, 407 patients had PTH and ECG data for analysis.

RESULTS

The QTc was longer in patients with elevated PTH levels compared with those without elevated PTH levels (451 ± 38.6 ms vs. 435 ± 29.8 ms; p < .001). The difference remained statistically significant after controlling for calcium, vitamin D, and estimated glomerular filtration rate (p = .007). Inclusion of left ventricular ejection fraction in the model attenuated the association (p = .054), suggesting that this finding may be partly driven by changes in cardiac structure.

CONCLUSIONS

In one of the largest series to examine PTH, calcium, and QT changes, we found that elevated PTH is associated with longer corrected QT interval independent of serum calcium concentration in ACS survivors.

Prediction of Both Electrical and Mechanical Reverse Remodeling on Acute Electrocardiogram Changes After Cardiac Resynchronization Therapy

BACKGROUND

The development of both electrical reverse remodeling and mechanical reverse remodeling (ERR+MRR) after cardiac resynchronization therapy (CRT) implantation could reduce the incidence of lethal arrhythmia, hence the prediction of ERR+MRR is clinically important.Methods and Results:Eighty-three patients (54 male; 67±12 years old) with CRT >6 months were enrolled. ERR was defined as baseline intrinsic QRS duration (iQRSd) shortening ≥10 ms in lead II on ECG after CRT, and MRR as improvement in LVEF ≥25% on echocardiography after CRT. Acute ECG changes were measured by comparing the pre-implant and immediate post-implant ECG. Ventricular arrhythmia episodes, including ventricular tachycardia and ventricular fibrillation, detected by the implanted device were recorded. Patients were classified as ERR only (n=12), MRR only (n=23), ERR+MRR (n=26), or non-responder (ERR- & MRR-, n=22). On multivariate regression analysis, difference between baseline intrinsic QRS and paced QRS duration (∆QRSd) >35 ms was a significant predictor of ERR+MRR (sensitivity, 68%; specificity, 64%; AUC, 0.7; P=0.003), and paced QTc >443 ms was a negative predictor of ERR+MRR (sensitivity, 78%; specificity, 60%; AUC, 0.7; P=0.002). On Cox proportional hazard modeling, ERR+MRR may reduce risk of ventricular arrhythma around 70% compared with non-responder (HR, 0.29; 95% CI: 0.13-0.65).

CONCLUSIONS

Acute ECG changes after CRT were useful predictors of ERR+MRR. ERR+MRR was also a protective factor for ventricular arrhythmia.

Changing characteristics and mode of death associated with chronic heart failure caused by left ventricular systolic dysfunction: a study across therapeutic eras

BACKGROUND

Therapies for patients with chronic heart failure caused by left ventricular systolic dysfunction have advanced substantially over recent decades. The cumulative effect of these therapies on mortality, mode of death, symptoms, and clinical characteristics has yet to be defined.

METHODS AND RESULTS

This study was a comparison of 2 prospective cohort studies of outpatients with chronic heart failure caused by left ventricular systolic dysfunction performed between 1993 and 1995 (historic cohort: n=281) and 2006 and 2009 (contemporary cohort: n=357). In the historic cohort, 83% were prescribed angiotensin-converting enzyme inhibitors and 8.5% were prescribed β-adrenoceptor antagonists, compared with 89% and 80%, respectively, in the contemporary cohort. Mortality rates over the first year of follow-up declined from 12.5% to 7.8% between eras (P=0.04), and sudden death contributed less to contemporary mortality (33.6% versus 12.7%; P<0.001). New York Heart Association class declined between eras (P<0.001). QTc dispersion across the chest leads declined from 85 ms (SD, 2) to 34 ms (SD, 1) and left ventricular end-diastolic dimensions declined from 65 mm (SD, 0.6) to 59 mm (SD, 0.5) (both P<0.001).

CONCLUSIONS

Survival has significantly improved in patients with chronic heart failure caused by left ventricular systolic dysfunction over the past 15 years; furthermore, sudden death makes a much smaller contribution to mortality, and noncardiac mortality is a correspondingly greater contribution. This has been accompanied by an improvement in symptoms and some markers of adverse electric and structural left ventricular remodeling.

Impact of coronary collateral circulation on QT dispersion in patients with coronary artery disease

OBJECTIVE

The aim of this study was to assess the effect of coronary collateral circulation (CCC) on QT dispersion (QTD) in coronary artery disease.

BACKGROUND

A prolonged QTD has been linked to increased heterogeneity of ventricular repolarization implicated in the genesis of ventricular arrhythmias and has been associated with an adverse prognosis in patients with coronary artery disease.

METHOD

CCC and corrected QTD (QTcD) were established in patients who had at least 85% stenosis in the left anterior descending coronary artery or in proximal part or in the body of the right coronary artery. Furthermore, left ventricular function score was determined for all the patients.

RESULTS

While CCC was not present (CCC grade 0) in 32 patients, 68 patients were observed with CCC (CCC grade > or =1). Mean QTcD was higher in patients who had CCC grade > or =1 than in patients with grade 0 (64.3+/-3.5 and 46.8+/-2.7, respectively, P=0.002). We detected a significant correlation between the collateral score and QTcD (r=0.354, P=0.001). CCC grade > or =1 patients had higher mean left ventricular function scores than grade 0 patients (P=0.048). Left ventricular function score and QTcD were observed to be correlated (r=0.200, P=0.046).

CONCLUSION

CCC in chronic coronary artery disease was not established to have a positive decreasing effect on QTcD. On the contrary, QTcD values were observed to be even higher in patients with well developed CCC. Further research including larger series and long-term follow-up is required to investigate this issue.

Prolongation of the QT-corrected interval during dobutamine stress echocardiography: a marker for ischemia

BACKGROUND

Dobutamine stress echocardiography (DSE) has become a very reliable non-invasive tool in the diagnosis of ischemic heart disease based on the determination of new wall motion abnormalities rather than electrocardiographic changes.

METHODS

In this study, we assessed the usefulness of the corrected QT (QTc) interval and delayed heart rate recovery in predicting ischemia during the infusion of dobutamine. In this retrospective analysis, we analyzed the electrocardiograms of 100 patients who underwent DSE for the diagnosis of coronary artery disease. The QTc interval obtained at peak heart rate during the infusion of dobutamine was compared with the QTc interval at rest.

RESULTS

A total of 32 patients had new wall motion abnormalities during DSE, suggestive of ischemia. In these patients, the mean QTc interval at rest was 442.6 ms as compared to 461.0 ms during the peak infusion of dobutamine (P<0.05). In contrast, there was no statistical difference between the mean QTc interval at rest and that noted during DSE in patients without ischemia (439.8 ms and 440.1 ms respectively, P =ls; NS). The QTc interval increased in 40% of patients with ischemia on DSE despite the absence of any accompanying ST-segment depressions. In addition, there was a statistically slower heart rate recovery. Changes in heart rate 2 min into recovery from peak heart rate were 7.3+/-9.5 beats/min in patients with ischemia compared to 12.5+/-11.9 beats/min in those without ischemia (P<0.027). A more significant change was noted 4 min into recovery when compared with the peak heart rate, 14.8+/-10 beats/min in patients with ischemia, compared with 22.2+/-15.7 beats/min in those without ischemia, (P<0.007).

CONCLUSIONS

These results suggest that the development of new wall motion abnormalities suggestive of ischemia during DSE is associated with prolongation of the QTc interval and delayed heart rate early in the recovery period. These two parameters should be further studied not only as additional markers in the identification of ischemia in patients referred for DSE but also to assess their potential significance during short- and long-term follow-up.