Effects of intracoronary low-dose enalaprilat as an adjunct to primary percutaneous transluminal coronary angiography in acute myocardial infarction

Pharmacologic Prevention of Myocardial Ischemia-Reperfusion Injury in Patients With Acute Coronary Syndrome Undergoing Percutaneous Coronary Intervention

ABSTRACT

Establishing efficient perfusion into the myocardium is the main purpose in patients with acute coronary syndrome, but the process of reperfusion is not without risk and can damage the myocardium paradoxically. Unfortunately, there is no effective treatment for reperfusion injury, and efforts to find an efficient preventive approach are still ongoing. In the past 3 decades, there have been many successful animal studies on how to prevent reperfusion injury; nonetheless, translation to the clinical setting has almost always proven disappointing. In this article, we review clinical studies on the prevention of reperfusion injury in patients with acute coronary syndrome undergoing primary percutaneous coronary intervention in a pharmacologic-based approach. We categorize all the agents that are evaluated for the prevention of myocardial reperfusion injury based on their mechanisms of action into 5 groups: drugs that can reduce oxidative stress, drugs that can affect cellular metabolism, rheological agents that target microvascular obstruction, anti-inflammatory agents, and agents with mixed mechanisms of action. Then, review all the clinical studies of these agents in the setting of primary percutaneous coronary intervention. Finally, we will discuss the possible reasons for the failure in translation of studies into practice and propose potential solutions to overcome this problem.

Extracellular signalling molecules in the ischaemic/reperfused heart - druggable and translatable for cardioprotection?

In patients with acute myocardial infarction, timely reperfusion is essential to limit infarct size. However, reperfusion also adds to myocardial injury. Brief episodes of ischaemia/reperfusion in the myocardium or on organ remote from the heart, before or shortly after sustained myocardial ischaemia effectively reduce infarct size, provided there is eventual reperfusion. Such conditioning phenomena have been established in many experimental studies and also translated to humans. The underlying signal transduction, that is the molecular identity of triggers, mediators and effectors, is not clear yet in detail, but several extracellular signalling molecules, such as adenosine, bradykinin and opioids, have been identified to contribute to cardioprotection by conditioning manoeuvres. Several trials have attempted the translation of cardioprotection by such autacoids into a clinical scenario of myocardial ischaemia and reperfusion. Adenosine and its selective agonists reduced infarct size in a few studies, but this benefit was not translated into improved clinical outcome. All studies with bradykinin or drugs which increase bradykinin's bioavailability reported reduced infarct size and some of them also improved clinical outcome. Synthetic opioid agonists did not result in a robust infarct size reduction, but this failure of translation may relate to the cardioprotective properties of the underlying anaesthesia per se or of the comparator drugs. The translation of findings in healthy, young animals with acute coronary occlusion/reperfusion to patients of older age, with a variety of co-morbidities and co-medications, suffering from different scenarios of myocardial ischaemia/reperfusion remains a challenge.

Pharmacological attenuation of myocardial reperfusion injury in a closed-chest porcine model: a systematic review

Myocardial ischemia-reperfusion injury is a clinical challenge in interventional cardiology, and at the moment, no pharmacological agent is universally accepted in the prevention. In order to prevent inappropriate clinical trials, a potential pharmacological agent should be proved reproducibly effective in clinically relevant experimental studies before initiation of human studies. The closed-chest porcine model is a promising experimental model of ischemia-reperfusion injury. The purpose of this systematic review was to describe the pharmacological treatments evaluated in the closed-chest porcine model and discuss different aspects of the model for future use. The systematic review was performed according to the PRISMA guidelines.

Intracoronary EnalaPrilat to Reduce MICROvascular Damage During Percutaneous Coronary Intervention (ProMicro) study

OBJECTIVES

This study investigated the influence of intracoronary enalaprilat on coronary microvascular function and peri-procedural outcome measures in patients with stable angina undergoing percutaneous coronary intervention (PCI).

BACKGROUND

Intracoronary angiotensin-converting enzyme inhibitors have been shown to relieve myocardial ischemia in stable patients and to improve epicardial flow in patients with ST-segment elevation myocardial infarction. Yet, it is still unclear whether these effects are mediated by a modulation of the coronary microcirculation.

METHODS

We randomly assigned 40 patients to receive either an intracoronary bolus of enalaprilat (50 μg) or placebo before elective PCI. The index of microvascular resistance was measured at baseline, 10 minutes after study drug administration, and after PCI. High-sensitivity cardiac troponin T was measured as a marker of myocardial injury.

RESULTS

Infusion of enalaprilat resulted in a significant reduction in index of microvascular resistance (27 ± 11 at baseline vs. 19 ± 9 after drug vs. 15 ± 8 after PCI), whereas a significant post-procedural increase in index of microvascular resistance levels was observed in the placebo group (24 ± 15 at baseline vs. 24 ± 15 after drug vs. 33 ± 19 after PCI). Index of microvascular resistance levels after PCI were significantly lower in the enalaprilat group (p < 0.001). Patients pre-treated with enalaprilat also showed lower peak values (mean: 21.7 ng/ml, range: 8.2 to 34.8 ng/ml vs. mean: 32.3 ng/ml, range: 12.6 to 65.2 ng/ml, p = 0.048) and peri-procedural increases of high-sensitivity cardiac troponin T (mean: 9.9 ng/ml, range: 2.7 to 19.0 ng/ml vs. mean: 26.6 ng/ml, range: 6.3 to 60.5 ng/ml, p = 0.025).

CONCLUSIONS

Intracoronary enalaprilat improves coronary microvascular function and protects myocardium from procedure-related injury in patients with coronary artery disease undergoing PCI. Larger studies are warranted to investigate whether these effects of enalaprilat could result into a significant clinical benefit.

The effect of enalapril on skin flap viability is independent of angiotensin II AT1 receptors

Random pattern skin flaps are still widely used in plastic surgery. However, necrosis in the distal portion resulting from ischemia is a serious problem, increasing the cost of treatment and hospitalization. To enhance skin flap viability, a variety of pharmacologic agents have been intensively investigated. The aim of this study was to assess the effect of enalapril (an angiotensin-converting enzyme inhibitor) and losartan (an angiotensin receptor blocker) in skin flap viability. Male rats of 200 to 250 g were used. Different doses of enalapril (5, 20, and 50 mg/kg) and losartan (5 mg/kg) were administrated 30 minutes prior to elevate the flap. Flap survival area was evaluated on the seventh postoperative day. Enalapril improved survival area in a dose-dependent manner, but losartan failed to improve survival area, which suggested that the effect of enalapril was not mediated through AT1 receptors.

Myocardial protection with enalaprilat in patients unresponsive to ischemic preconditioning during percutaneous coronary intervention

Cardioprotection due to angiotensin enzyme inhibitors is attributed, at least in part, to the inhibition of bradykinin breakdown and the preconditioning effect of the elevated endogenous bradykinin level. We have previously shown that in patients undergoing percutaneous coronary intervention, one 120-second balloon inflation is insufficient to precondition the heart. The objective of the present study was to examine whether the administration of enalaprilat to these patients results in protection. Twenty patients underwent two 120-second coronary artery occlusions separated by a reperfusion interval of 10 min. Ten patients were given 50 µg·min–1 enalaprilat in an intracoronary infusion between the balloon inflations, whereas the others received an infusion of saline. In the latter control patients, there were no significant differences in ST-segment elevation between the consecutive occlusions (peak ST: 1.61 ± 0.17 vs. 1.61 ± 0.16 mV; time to reach 0.5 mV ST elevation: 16 ± 4 vs. 22 ± 7 s; mean ST: 1.03 ± 0.12 vs. 1.02 ± 0.11 mV). In the patients who received enalaprilat before the second balloon inflation, the ST-segment elevation was significantly less pronounced and slower during the second inflation than during the first (peak ST: 1.80 ± 0.18 vs. 1.41 ± 0.19 mV; time to reach 0.5 mV ST elevation: 18 ± 4 vs. 30 ± 4 s; mean ST: 1.04 ± 0.11 vs. 0.85 ± 0.14 mV). We conclude that enalaprilat administered during percutaneous coronary intervention provides protection to patients who do not have a protective response to the initial balloon inflation.

Low doses of intracoronary enalaprilat suppress reperfusion-associated ventricular arrhythmias after primary percutaneous coronary interventions for acute myocardial infarction

BACKGROUND

In the era of early reperfusion therapy, life-threatening ventricular arrhythmias (VA) remain common after recanalization of an occluded coronary artery. Experimental studies reported that angiotensin-converting (ACE) inhibitors suppress reperfusion-induced VA. However, whether ACE inhibitors lower the incidence of reperfusion clinical VA is unknown. We examined the effects of low doses of intracoronary (i.c.) enalaprilat (EN) as an adjunct to direct percutaneous coronary interventions (PCI) on reperfusion VA in the acute phase of myocardial infarction (MI).

METHODS

We randomly assigned 22 patients with a first acute MI, who underwent successful direct PCI, to EN, 50 mug, i.c., or placebo (PL), administered immediately after reperfusion. VA were manually edited and counted from 24-hour Holter recordings begun upon hospital admission.

RESULTS

There were no significant between-groups differences in clinical characteristics. Mean RR interval before and after PCI, and the incidence of VA before PCI were similar in both groups. After PCI the incidence of reperfusion-induced VA was significantly lower in the EN-treated group (VPB/h: PL 29.9 +/- 12 vs EN 43.2 +/- 42, P < 0.05; couplets/h: EN 0.9 +/- 0.7 vs PL 4.1 +/- 5.0, P < 0.01; triplets/h: EN 0.3 +/- 0.2 vs PL 1.2 +/- 1.5, P < 0.05; ventricular tachycardia/h: EN 0.3 +/- 0.1 vs PL 0.8 +/- 0.5, P < 0.01).

CONCLUSIONS

Compared with PL, i.c. EN significantly lowered the incidence of reperfusion-associated VA. This previously unrecognized antiarrhythmic effect might be an important therapeutic benefit conferred by ACE inhibitors, beyond limitation of infarct size.

Reperfusion injury as a therapeutic challenge in patients with acute myocardial infarction

Cardiomyocyte death secondary to transient ischemia occurs mainly during the first minutes of reperfusion, in the form of contraction band necrosis involving sarcolemmal rupture. Cardiomyocyte hypercontracture caused by re-energisation and pH recovery in the presence of impaired cytosolic Ca(2+) control as well as calpain-mediated cytoskeletal fragility play prominent roles in this type of cell death. Hypercontracture can propagate to adjacent cells through gap junctions. More recently, opening of the mitochondrial permeability transition pore has been shown to participate in reperfusion-induced necrosis, although its precise relation with hypercontracture has not been established. Experimental studies have convincingly demonstrated that infarct size can be markedly reduced by therapeutic interventions applied at the time of reperfusion, including contractile blockers, inhibitors of Na(+)/Ca(2+) exchange, gap junction blockers, or particulate guanylyl cyclase agonists. However, in most cases drugs for use in humans have not been developed and tested for these targets, while the effect of existing drugs with potential cardioprotective effect is not well established or understood. Research effort should be addressed to elucidate the unsolved issues of the molecular mechanisms of reperfusion-induced cell death, to identify and validate new targets and to develop appropriate drugs. The potential benefits of limiting infarct size in patients with acute myocardial infarction receiving reperfusion therapy are enormous.

Effects of Intracoronary Low-Dose Enalaprilat on Ventricular Repolarization Dynamics After Direct Percutaneous Intervention for Acute Myocardial Infarction

BACKGROUND

Data from animal models suggest that inhibition of angiotensin converting enzymes result in an increased ventricular electrical stability after reperfusion in acute myocardial infarction (MI). As electrical stability is largely dependent on ventricular repolarization, we sought to determine the impact of low-dose intracoronary (i.c.) application of enalaprilat (EN) as an adjunct to direct primary coronary intervention (PCI) on QT dynamics in the acute phase of MI.

METHODS

Twenty-two consecutive patients with a first acute MI who underwent successful direct PCI (TIMI 3 flow) were randomized to i.c. EN (50 microg) or placebo/saline (PL), given immediately after reopening of the infarct vessel. On hospital admission, a 24-hour-Holter-electrocardiogram (ECG) was initiated. Slopes of the linear QT/RR regression were determined for the time intervals before reperfusion and after reperfusion.

RESULTS

A total of 7 patients in the EN group and 8 patients in the PL group had valid ECG recordings for beat-to-beat QT analysis. Mean RR interval and mean QT interval were not significantly different between the EN and the PL groups both before and after PCI. There were also no significant differences regarding QT/RR slopes between EN and PL groups before PCI. After PCI, QT/RR slopes significantly decreased in the EN group (0.169 +/- 0.04 to 0.121 +/- 0.03; P < 0.01), whereas there were no significant alterations in the PL group (0.175 +/- 0.04 to 0.171 +/- 0.03; P = ns).

CONCLUSIONS

Intracoronary EN therapy as an adjunct to direct PCI significantly decreases QT/RR slopes, suggesting a normalization of the coupling between heart rate and repolarization by improving electrical restitution. Thus, our findings offer new insights into possible beneficial effects of ACE inhibition on cardiac electrical stability in acute MI.

Intracoronary enalaprilat during angioplasty for acute myocardial infarction: alleviation of postischaemic neurohumoral and inflammatory stress?

AIM

Reperfusion after myocardial ischaemia is associated with a distinct ischaemia/reperfusion injury. Since ACE-inhibition, beyond its influence on cardiac angiotensin II formation and kinin metabolism, has been shown to be cardioprotective by decreasing leucocyte adhesion and endothelin-1 (ET-1) release, we investigated the effects of intracoronary (i.c.) enalaprilat during primary angioplasty in acute myocardial infarction.

METHODS AND RESULTS

Twenty-two patients were randomized to receive i.c. enalaprilat (50 micro g) or placebo immediately after reopening of the infarct-related artery (IRA). Plasma concentrations of soluble L-selectin, P-selectin, intercellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), ET-1 and nitric oxide metabolite concentrations (NOx) were measured in pulmonary arterial blood. Coronary blood flow was assessed using corrected thrombolysis in myocardial infarction (TIMI) frame counts (CTFC). During reperfusion, there was a significant increase in sL-selectin, sP-selectin and ET-1 in the placebo group, which was greatly diminished by enalaprilat. Levels of sVCAM-1 and sICAM-1 were not affected in either group. CTFC in the placebo group remained higher than normal in both the IRA and nonculprit vessels, whereas myocardial blood flow improved with enalaprilat.

CONCLUSION

Enalaprilat as adjunct to primary angioplasty might be a protective approach to prevent leucocyte adhesion and the release of ET-1, thereby improving coronary blood flow.

Tachyarrhythmias in percutaneous coronary interventions

Accompanying the clear benefits, there are certain risks of tachyarrhythmias in percutaneous coronary interventions (PCI), including serious ventricular arrhythmias and atrial fibrillation (AF). Ventricular arrhythmias may result from excess catheter manipulation, intracoronary dye injection, new ischemic events, or reperfusion. In patients with heart failure such kind of arrhythmias can occur more frequently. Atrial dysfunction, sino-atrial and nodal ischemia, congestive heart failure, sympathetic stimulation, iatrogenic factors are the possible causes of AF especially in patients undergoing primary PCI. Atrial fibrillation, on the other hand, can cause clinical squeal in the setting of a rapid ventricular response or if the loss of atrial systole results in hypotension, as in a patient with mitral stenosis or diastolic ventricular dysfunction. Majority of the ventricular arrhythmias and AF tend to revert spontaneously. However, the special treatment must be given, when necessary.

The calcium sensitizer levosimendan improves the function of stunned myocardium after percutaneous transluminal coronary angioplasty in acute myocardial ischemia

OBJECTIVES

We assessed the effects of levosimendan on left ventricular (LV) function in patients with acute myocardial ischemia and after coronary angioplasty.

BACKGROUND

The calcium sensitizer levosimendan improves the function of myocardium in experimental stunning.

METHODS

Twenty-four patients with an acute coronary syndrome underwent angioplasty followed by double-blinded, randomized treatment with 24 microg/kg of levosimendan (n = 16) or placebo (n = 8). Left ventricular pressures and volumes were recorded by cineventriculography and micromanometer-tipped catheters 10 min after angioplasty before drug administration (baseline) and 20 min after drug administration. Left ventricular function was assessed by the pressure-volume loop, and regional function analysis by the Slager method.

RESULTS

The number of hypokinetic segments decreased with levosimendan, from 8.9 +/- 0.9 to 6.5 +/- 1.1 (mean +/- SEM), as compared with an increase from 7.8 +/- 1.0 to 8.5 +/- 1.1 with placebo (p = 0.016). A leftward and/or upward shift of the systolic part of the pressure-volume loop, indicating improved systolic function, was observed in eight of 16 of the levosimendan-treated and one of eight of the placebo patients (p = 0.178). In addition, the single-beat elastance was increased by levosimendan (p = 0.045). The pressure-volume area (p = 0.001), end-systolic pressure (p = 0.002), and volume index (p < 0.001) were decreased by levosimendan, but there was no change in the end-systolic pressure-volume ratio. End-diastolic pressure remained unchanged, whereas the end-diastolic volume index was decreased by levosimendan (p = 0.002). The time constant of isovolumic LV pressure fall decreased with levosimendan (p = 0.001).

CONCLUSIONS

Levosimendan improved the function of stunned myocardium without obvious impairment of diastolic function.

Effect of ACE-inhibitor ramiprilat and AT1-receptor antagonist candesartan on cardiac norepinephrine release: comparison between ischemic and nonischemic conditions

ACE-inhibitors and AT -receptor antagonists may exert part of their pharmacological actions by interference with angiotensin-and/or bradykinin-mediated prejunctional stimulation of cardiac norepinephrine release. As endogenous formation of angiotensin and bradykinin is increased in ischemia, we investigated the effects of the ACE-inhibitor ramiprilat and the AT -receptor antagonist candesartan on cardiac norepinephrine release in isolated perfused rat hearts, under nonischemic and stop-flow conditions. Exocytotic release of endogenous norepinephrine was induced by electrical field stimulation and measured by HPLC. Paired stimulations were applied in each heart to obtain an intraindividual comparison of the effect of the pharmacological agent on norepinephrine release with the release under baseline conditions. The ACE-inhibitor ramiprilat (0.1-10 nM) and the AT -receptor antagonist candesartan (1-100 nM) were studied during normal flow or in the fourth minute of stop-flow. Under nonischemic conditions, the ACE-inhibitor slightly reduced norepinephrine release at the highest concentration, while the AT -receptor antagonist did not influence norepinephrine release in normoxia. Conversely, both substances significantly increased norepinephrine release during ischemia. Augmentation of norepinephrine release in ischemia by ramiprilat and candesartan was blocked by the bradykinin B -receptor antagonist HOE 140 and, in case of candesartan, by the AT -receptor antagonist PD 123319. The ACE-inhibitor ramiprilat and AT -receptor antagonist candesartan enhance cardiac norepinephrine release selectively in ischemia by stimulating presynaptic bradykinin B -receptors. Regarding the AT -receptor antagonist, AT -receptor activation is also involved in bradykinin-mediated prejunctional stimulation.