The effect of verapamil on the restoration of myocardial perfusion and functional recovery in patients with angiographic no-reflow after primary percutaneous coronary intervention

Pathophysiology, Diagnosis, and Management of Coronary No-Reflow Phenomenon

Coronary no-reflow phenomenon is a lethal mechanism of ongoing myocardial injury following successful revascularization of an infarct-related coronary artery. Incidence of this phenomenon is high following percutaneous intervention and is associated with adverse in-hospital and long-term outcomes. Several mechanisms such as ischemia-reperfusion injury and distal microthromboembolism in genetically susceptible patients and those with preexisting endothelial dysfunction have been implicated. However, the exact mechanism in humans is still poorly understood. Several investigative and treatment strategies within and outside the cardiac catheterization laboratory have been proposed, but they have not uniformly shown success in reducing mortality or in preventing adverse left ventricular remodeling resulting from this condition. The aim of this article is to provide a brief and concise review of the current understanding of the pathophysiology, clinical predictors, and investigations and management of coronary no-reflow phenomenon.

Pathophysiology, Diagnosis, and Management of Coronary No-Reflow Phenomenon

Coronary no-reflow phenomenon is a lethal mechanism of ongoing myocardial injury, following successful revascularization of an infarct-related coronary artery. Incidence of this phenomenon is high following percutaneous intervention, and is associated with adverse in-hospital and long-term outcomes. Several mechanisms such as ischemia-reperfusion injury and distal microthromboembolism in genetically susceptible patients and those with preexisting endothelial dysfunction have been implicated. However, the exact mechanism in humans is still poorly understood. Several investigative and treatment strategies within and outside the cardiac catheterization laboratory have been proposed, but have not uniformly shown success in reducing mortality or in preventing adverse left ventricular remodeling resulting from this condition. The aim of this article is to provide a brief and concise review of the current understanding of the pathophysiology, clinical predictors, and investigations and management of coronary no-reflow phenomenon.

Management of No-Reflow Phenomenon in the Catheterization Laboratory

At the conclusion of a primary percutaneous coronary intervention for ST-segment elevation myocardial infarction, and after the cardiologist makes certain that there is no residual stenosis following stenting, assessment of coronary flow becomes the top priority. The presence of no-reflow is a serious prognostic sign. No-reflow can result in poor healing of the infarct and adverse left ventricular remodeling, increasing the risk for major adverse cardiac events, including congestive heart failure and death. To achieve normal flow, features associated with a high incidence of no-reflow must be anticipated, and measures must be undertaken to prevent its occurrence. In this review, the authors discuss various preventive strategies for no-reflow as well as pharmacological and nonpharmacological interventions that improve coronary blood flow, such as intracoronary adenosine and nitroprusside. Nonpharmacological therapies, such as induced hypothermia, were successful in animal studies, but their effectiveness in reducing no-reflow in humans remains to be determined.

Verapamil reverses myocardial no-reflow after primary percutaneous coronary intervention in patients with acute myocardial infarction

The present study evaluated the efficacy of intracoronary administration of verapamil to attenuate the no-reflow phenomenon following the primary percutaneous coronary intervention (PCI) in patients with the ST-segment elevation acute myocardial infarction (STEMI). A total of 201 patients with STEMI who underwent primary PCI within 12 h from the beginning of the heart attack were included. The no-reflow phenomenon was defined as substantial coronary anterograde flow of TIMI ≤2. Verapamil (100-200 μg) was injected into coronary artery immediately after no-reflow; the coronary arteriography was repeated later. Hundred and ninety-eight patients with STEMI successfully underwent primary PCI, and 246 stents were implanted with the average of 1.2 stents per patient. No-reflow occurred in 25 out of 198 patients (12.6%). Twenty-one (84%) patients developed the flow of TIMI ≥3 after intracoronary administration of verapamil, as revealed by repeated coronary angiography. Two patients developed transient hypotension which normalized without treatment within 3-5 min. Three patients showed sinus bradycardia, in one patient there was transient II sinoatrial block, and one patient developed type 1 atrioventricular block. All adverse effects were alleviated after intravenous injection of atropine (0.5-1 mg). In conclusion, the no-reflow phenomenon following primary PCI in patients with STEMI is significantly improved by intracoronary administration of verapamil which is useful to reduce cardiovascular events during operation.

Imaging the myocardial microcirculation post-myocardial infarction

The myocardial microcirculation provides the vital pressure control and metabolic homeostasis for normal muscle function. Microvascular dysfunction is implicated in chronic cardiac disease and can signify higher risk, but its effect in acute myocardial infarction (AMI) can be profound. Modern management of AMI is focussed entirely on timely epicardial coronary patency, but as a result can leave microcirculatory devastation in its wake. The 'no-reflow' phenomenon occurs in up to 40 % of those successfully reperfused following an ST-elevation AMI (STEMI), and reflects significant microvessel injury that at its most severe involves both microvascular obstruction (MVO) and intramyocardial haemorrhage. Myocardial contrast echocardiography and cardiac magnetic resonance imaging have both led the field in establishing MVO as the prime determinant of adverse left ventricular (LV) remodeling, LV dysfunction, heart failure and increased mortality. These imaging techniques will be essential to support future research endeavours and shift focus to the maintenance of microvascular flow in AMI.

Diannexin reduces no-reflow after reperfusion in rabbits with large ischemic myocardial risk zones

INTRODUCTION AND AIMS

In patients with ST-segment elevation myocardial infarction who receive percutaneous coronary intervention and stenting, a large zone with no-reflow is associated with adverse outcomes. During myocardial ischemia/reperfusion, phosphatidylserine (PS) translocates to the surface of endothelial cells triggering attachment of platelets and leukocytes, thus impairing microvascular blood flow. Diannexin, a recombinant dimer of the endogenous human annexin V protein, binds PS and thus inhibits the adverse effects of PS. It has been shown to attenuate postischemic reperfusion injury in several experimental models. We speculated that Diannexin would reduce no-reflow in the heart after coronary artery occlusion (CAO) and reperfusion. Rabbits received: (1) Diannexin 5 min pre-CAO (diannexin pre ischemia [DPI], 400 μg/kg, n = 17), or (2) Diannexin 5 min pre-coronary reperfusion (diannexin pre reperfusion [DPR], 400 μg/kg, n = 20), or (3) saline (Cont, n = 18), with 30 min CAO and 3 h reperfusion. In a secondary analysis, rabbits were divided into two groups based on the overall average risk zone size of 29% of the left ventricle (LV): small (<29% of LV) and large (>29% of LV).

RESULTS

Overall, risk zones and infarct size, and the no-reflow zone were similar in all groups. In hearts with large risk zones the no-reflow area was significantly smaller in both drug-treated groups (DPI, 22 ± 5% and DPR, 22 ± 3% vs. control 40 ± 3%, P < 0.006), the hemorrhagic areas were significantly smaller, and infarct size was reduced at the P < 0.06 level compared with control. In animals with small risk zones there were no significant differences. Diannexin treatment did not affect hemodynamics or LV function.

CONCLUSION

Diannexin was cardioprotective in rabbits with a severe ischemic insult. This is important, because large infarcts accompanied by no-reflow in humans are associated with increased complications. In animals with small risk zones, no significant drug effect was observed.

Pathogenesis of myocardial ischemia-reperfusion injury and rationale for therapy

Since the initial description of the phenomenon by Jennings et al 50 years ago, our understanding of the underlying mechanisms of reperfusion injury has grown significantly. Its pathogenesis reflects the confluence of multiple pathways, including ion channels, reactive oxygen species, inflammation, and endothelial dysfunction. The purposes of this review are to examine the current state of understanding of ischemia-reperfusion injury, as well as to highlight recent interventions aimed at this heretofore elusive target. In conclusion, despite its complexity our ongoing efforts to mitigate this form of injury should not be deterred, because nearly 2 million patients annually undergo either spontaneous (in the form of acute myocardial infarction) or iatrogenic (in the context of cardioplegic arrest) ischemia-reperfusion.

Intracoronary Vasodilators for the No-Reflow Phenomenon

Objective:

To review the literature relating to the use of intracoronary vasodilators to prevent and/or treat the no-reflow phenomenon in patients undergoing percutaneous coronary intervention (PCI).

Data Sources:

A literature search was conducted using MEDLINE (1966–March 2008) and Science Citation Index (1945–March 2008) using the search terms vasodilators, no-reflow, and intracoronary.

Study Selection and Data Extraction:

English-language clinical trials and case series were selected from articles retrieved. References of reviewed articles were examined for additional sources. Studies relating to the use of intracoronary vasodilators in the prevention and/or treatment of no-reflow in PCI were evaluated for safety and efficacy data. Articles relating to agents not available in the US were excluded.

Data Synthesis:

Evidence of intracoronary adenosine's utility in no-reflow treatment is limited. Its use in no-reflow prevention was associated with outcomes ranging from no difference to nearly an 88% reduction in no-reflow development; the drug was generally well tolerated. No-reflow treatment with intracoronary verapamil improved flow in 87–100% of cases. Preventive trials with verapamil failed to demonstrate efficacy. Atrioventricular block requiring treatment was the most commonly reported adverse event with intracoronary verapamil. Literature on intracoronary diltiazem and intracoronary nicardipine is limited. Both agents produced greater than 95% efficacy in no-reflow treatment, while prevention studies found no-reflow developing in less than 4% of patients. Although adverse event reporting was limited, hemodynamic instability was noted in patients receiving diltiazem. Response rates ranged from 73% to 100% when intracoronary nitroprusside was studied as treatment for no-reflow associated with acute myocardial infarction (AMI). Systemic hypotension was noted with nitroprusside administration.

Conclusions:

The available data are predominately from case series and retrospective reviews. Prevention of no-reflow with intracoronary vasodilators in elective PCI is not warranted. Nitroprusside should be considered first-line treatment in no-reflow associated with AMI.

No-reflow phenomenon and prognosis in patients with acute myocardial infarction

The rapid restoration of coronary flow to the jeopardized myocardium has become an essential part of therapy after acute myocardial infarction. Despite an open infarct-related artery, breakdown of or obstruction to coronary microvasculature can markedly reduce blood flow to the infarct zone. This effect is known as the no-reflow phenomenon. Advances in imaging modalities have improved visualization of no reflow, showing its frequency to be higher than was estimated by clinical judgment alone. This phenomenon is important because it correlates with infarct size and provides useful prognostic information. No reflow is associated with reduced left ventricular ejection fraction, left ventricular remodeling, and poor clinical outcomes, placing patients with this effect in a high-risk group among reperfused patients. The focus of reperfusion therapy is shifting towards improved myocardial perfusion, which could promote functional recovery of viable muscle, reduce infarct expansion, and increase the delivery of blood-borne components, thereby accelerating the healing process. Various pharmacologic interventions and catheter-based devices to retrieve embolic materials have been proposed. Further studies to improve understanding of the pathophysiology of microvascular dysfunction will, however, help in the further development of preventive and therapeutic strategies. In this article, I discuss in depth the data available on the no-reflow phenomenon.