Effects of early captopril therapy after myocardial infarction on the incidence of late potentials

Valsartan Upregulates Kir2.1 in Rats Suffering from Myocardial Infarction via Casein Kinase 2

Purpose

Myocardial infarction (MI) results in an increased susceptibility to ventricular arrhythmias, due in part to decreased inward-rectifier K+ current (IK1), which is mediated primarily by the Kir2.1 protein. The use of renin-angiotensin-aldosterone system antagonists is associated with a reduced incidence of ventricular arrhythmias. Casein kinase 2 (CK2) binds and phosphorylates SP1, a transcription factor of KCNJ2 that encodes Kir2.1. Whether valsartan represses CK2 activation to ameliorate IK1 remodeling following MI remains unclear.

Methods

Wistar rats suffering from MI received either valsartan or saline for 7 days. The protein levels of CK2 and Kir2.1 were each detected via a Western blot analysis. The mRNA levels of CK2 and Kir2.1 were each examined via quantitative real-time PCR.

Results

CK2 expression was higher at the infarct border; and was accompanied by a depressed IK1/Kir2.1 protein level. Additionally, CK2 overexpression suppressed KCNJ2/Kir2.1 expression. By contrast, CK2 inhibition enhanced KCNJ2/Kir2.1 expression, establishing that CK2 regulates KCNJ2 expression. Among the rats suffering from MI, valsartan reduced CK2 expression and increased Kir2.1 expression compared with the rats that received saline treatment. In vitro, hypoxia increased CK2 expression and valsartan inhibited CK2 expression. The over-expression of CK2 in cells treated with valsartan abrogated its beneficial effect on KCNJ2/Kir2.1.

Conclusions

AT1 receptor antagonist valsartan reduces CK2 activation, increases Kir2.1 expression and thereby ameliorates IK1 remodeling after MI in the rat model.

The association between early ventricular arrhythmias, renin-angiotensin-aldosterone system antagonism, and mortality in patients with ST-segment-elevation myocardial infarction: Insights from Global Use of Strategies to Open coronary arteries (GUSTO) V

BACKGROUND

The long-term prognostic significance of early (<48 hours) ventricular fibrillation (VF) or sustained ventricular tachycardia (VT) in patients with an acute myocardial infarction remains controversial. Emerging data suggest that some of the benefit of renin-angiotensin-aldosterone system (RAAS) antagonism may be derived from a reduction in the incidence of these arrhythmias in the setting of acute myocardial infarction.

METHODS

We assessed the relationship between early VF/VT (defined as within 48 hours after admission) and mortality in 16,588 patients from global use of strategies to open coronary arteries (GUSTO) V trial. Furthermore, we examined the relationship between baseline use of angiotensin-converting enzyme inhibitor (ACEI)/angiotensin receptor blocker (ARB), early VF/VT, and mortality.

RESULTS

Early VF or VT occurred in 732 (4.4%) patients. Compared to patients without VF/VT, those experiencing early VF or VT had a significant increase in 30-day mortality (22% vs 5%, P < .001). Baseline use of an ACEI/ARB was associated with a decreased incidence of early VF/VT (odds ratio 0.65, 0.47-0.89, P = .008). A lower 30-day mortality was seen in patients with early VF/VT on baseline ACEI/ARB compared with patients with early VF/VT not receiving an ACEI/ARB at baseline (17.7% vs 24.2%, respectively, P = .04). The association between baseline RAAS antagonism and mortality persisted after adjustment for multiple confounders.

CONCLUSIONS

In patients presenting with acute myocardial infarction, early VF/VT identifies those at increased risk for 30-day mortality. Baseline use of RAAS antagonists is associated with a reduced incidence of malignant arrhythmias. Identifying how this association impacts short-term mortality in this patient population requires further prospective evaluation.

Effects of early losartan therapy on ventricular late potentials in acute myocardial infarction

BACKGROUND

Ventricular late potentials (LPs) obtained by the signal-averaged electrocardiogram (SAECG) have prognostic significance as independent predictors of arrhythmic events after an acute myocardial infarction (AMI). Angiotensin receptor blockers reduce the overall mortality and risk of sudden cardiac death in postinfarction patients. The aim of this study was to investigate the effect of early losartan therapy on ventricular LPs, a noninvasive method for the evaluation of arrhythmogenic substrates in AMI patients.

METHODS

The study included 97 patients with their first AMI. Forty-eight patients (39 men and 9 women, aged 58.8 +/- 13.19 years), received early losartan therapy. The control group consisted of 49 patients (38 men and 11 women, aged 59.55 +/- 11.0 years), did not received early losartan therapy. The SAECG was performed at admission and day 14.

RESULTS

The baseline clinical, angiographic characteristics, and reperfusion methods were similar in both groups. The baseline SAECG findings were also similar in the two groups. There was a significant decrease in the rate of LP, between the first and last SAECG recordings, after reperfusion therapy in the losartan group. All of the parameters of LPs were significantly improved in the losartan group on the last SAECG recordings.

CONCLUSION

The results of this study showed that losartan treatment, early after an AMI, reduced the incidence of LP and may thus favorably affect arrhythmia substrates.

Evaluation of the Rabbit Purkinje Fibre Assay as an in vitro Tool for Assessing the Risk of Drug-Induced Torsades de Pointes in Humans

BACKGROUND

The issue of drug-induced QT interval prolongation and torsades de pointes represents a major concern for pharmaceutical development. In this investigation, we examined the value of the isolated rabbit Purkinje fibre as an in vitro action potential (AP) assay to predict the potential of drugs to induce these undesirable adverse effects.

METHODS

First, we categorised the proarrhythmic risk of 26 medicinal products based on proportional reporting ratios for these two adverse events recorded in a US FDA database (Spontaneous Reporting System/Adverse Event Reporting System). Second, we measured drug effects on AP in rabbit Purkinje fibres. Finally, the results of the two analyses were compared to evaluate the predictive value of the in vitro assay.

RESULTS

Analysis of the clinical data classified the drugs into 14 positive, 7 negative and 5 questionable for proarrhythmic risk. Based on in vitro electrophysiological profiles, the drugs were grouped into four categories: (i) profile 1 drugs prolong repolarisation without slowing depolarisation; (ii) profile 2 drugs prolong repolarisation and also slow depolarisation; (iii) profile 3 drugs shorten repolarisation; and (iv) profile 4 drugs are without effects. All 14 clinical-positive drugs fell into profiles 1 or 2 (prolongers) with low safety margins (except probucol, which showed no effect, probably because of its low solubility). Clinical-negative drugs belonged mostly to profiles 3 or 4 (non-prolongers) [except clemastine and amlodipine, which were prolongers but had large safety margins]. Clinical-questionable drugs either did not prolong or prolonged slightly but produced additional electrophysiological effects opposing prolongation.

CONCLUSION

The rabbit Purkinje fibre is a valuable assay for evaluating the proarrhythmic liability of pharmaceuticals as it can reveal complex electrophysiological profiles that modulate repolarisation delay.