Treatment of no-reflow and impaired flow with the nitric oxide donor nitroprusside following percutaneous coronary interventions: initial human clinical experience

No-Reflow Prediction in Acute Coronary Syndrome During Percutaneous Coronary Intervention: The NORPACS Risk Score

BACKGROUND

Suboptimal coronary reperfusion (no reflow) is common in acute coronary syndrome percutaneous coronary intervention (PCI) and is associated with poor outcomes. We aimed to develop and externally validate a clinical risk score for angiographic no reflow for use following angiography and before PCI.

METHODS

We developed and externally validated a logistic regression model for prediction of no reflow among adult patients undergoing PCI for acute coronary syndrome using data from the Melbourne Interventional Group PCI registry (2005-2020; development cohort) and the British Cardiovascular Interventional Society PCI registry (2006-2020; external validation cohort).

RESULTS

A total of 30 561 patients (mean age, 64.1 years; 24% women) were included in the Melbourne Interventional Group development cohort and 440 256 patients (mean age, 64.9 years; 27% women) in the British Cardiovascular Interventional Society external validation cohort. The primary outcome (no reflow) occurred in 4.1% (1249 patients) and 9.4% (41 222 patients) of the development and validation cohorts, respectively. From 33 candidate predictor variables, 6 final variables were selected by an adaptive least absolute shrinkage and selection operator regression model for inclusion (cardiogenic shock, ST-segment-elevation myocardial infarction with symptom onset >195 minutes pre-PCI, estimated stent length ≥20 mm, vessel diameter <2.5 mm, pre-PCI Thrombolysis in Myocardial Infarction flow <3, and lesion location). Model discrimination was very good (development C statistic, 0.808; validation C statistic, 0.741) with excellent calibration. Patients with a score of ≥8 points had a 22% and 27% risk of no reflow in the development and validation cohorts, respectively.

CONCLUSIONS

The no-reflow prediction in acute coronary syndrome risk score is a simple count-based scoring system based on 6 parameters available before PCI to predict the risk of no reflow. This score could be useful in guiding preventative treatment and future trials.

A historical literature review of coronary microvascular obstruction and intra-myocardial hemorrhage as functional/structural phenomena

The analysis of experimental data demonstrates that platelets and neutrophils are involved in the no-reflow phenomenon, also known as microvascular obstruction (MVO). However, studies performed in the isolated perfused hearts subjected to ischemia/reperfusion (I/R) do not suggest the involvement of microembolization and microthrombi in this phenomenon. The intracoronary administration of alteplase has been found to have no effect on the occurrence of MVO in patients with acute myocardial infarction. Consequently, the major events preceding the appearance of MVO in coronary arteries are independent of microthrombi, platelets, and neutrophils. Endothelial cells appear to be the target where ischemia can disrupt the endothelium-dependent vasodilation of coronary arteries. However, reperfusion triggers more pronounced damage, possibly mediated by pyroptosis. MVO and intra-myocardial hemorrhage contribute to the adverse post-infarction myocardial remodeling. Therefore, pharmacological agents used to treat MVO should prevent endothelial injury and induce relaxation of smooth muscles. Ischemic conditioning protocols have been shown to prevent MVO, with L-type Ca ²⁺ channel blockers appearing the most effective in treating MVO.

Saphenous Vein Graft Intervention

Even though saphenous vein grafts (SVGs) are the most commonly used surgical conduits, their long-term patency is limited by accelerated atherosclerosis often resulting in acute coronary syndrome or asymptomatic occlusion. SVG intervention is associated with 2 significant challenges: a significant risk of distal embolization with resultant periprocedural myocardial infarction in the short-term and restenosis in the long-term. Several individual trials have compared bare metal stents with drug-eluting stents for SVG intervention. This review article discusses the pathophysiology of SVG lesions, indications for SVG intervention, and the challenges encountered, and also technical considerations for SVG intervention and the supporting evidence.

Mechanism and potential treatment of the "no reflow" phenomenon after acute myocardial infarction: role of pericytes and GPR39

The "no reflow" phenomenon, where the coronary artery is patent after treatment of acute myocardial infarction (AMI) but tissue perfusion is not restored, is associated with worse outcome. The mechanism of no reflow is unknown. We hypothesized that pericytes contraction, in an attempt to maintain a constant capillary hydrostatic pressure during reduced coronary perfusion pressure, causes capillary constriction leading to no reflow and that this effect is mediated through the orphan receptor, GPR39, present in pericytes. We created AMI (coronary occlusion followed by reperfusion) in GPR39 knock out mice and littermate controls. In a separate set of experiments, we treated wild-type mice undergoing coronary occlusion with vehicle or VC43, a specific inhibitor of GPR39, before reperfusion. We found that no reflow zones were significantly smaller in the GPR39 knockouts compared with controls. Both no reflow and infarct size were also markedly smaller in animals treated with VC43 compared with vehicle. Immunohistochemistry revealed greater capillary density and larger capillary diameter at pericyte locations in the GPR39-knockout and VC43-treated mice compared with controls. We conclude that GPR39-mediated pericyte contraction during reduced coronary perfusion pressure causes capillary constriction resulting in no reflow during AMI and that smaller no reflow zones in GPR39-knockout and VC43-treated animals are associated with smaller infarct sizes. These results elucidate the mechanism of no reflow in AMI, as well as providing a therapeutic pathway for the condition.NEW & NOTEWORTHY The mechanism of "no reflow" phenomenon, where the coronary artery is patent after treatment of acute myocardial infarction but tissue perfusion is not restored, is unknown. This condition is associated with worse outcome. Here, we show that GPR39-mediated pericyte contraction during reduced coronary perfusion pressure causes capillary constriction resulting in no reflow. Smaller no-reflow zones in GPR39-knockout animals and those treated with a GPR39 inhibitor are associated with smaller infarct size. These results could have important therapeutic implications.

The effectiveness of alprostadil in treating coronary microcirculation dysfunction following ST-segment elevation myocardial infarction in a pig model

Though alprostadil has been reported to improve the impaired microcirculation of patients with pulmonary arterial hypertension, its effectiveness as a treatment for coronary microvasculature dysfunction (CMD) following ST-segment elevation myocardial infarction (STEMI) is unknown. A total of 18 miniature pigs with CMD following STEMI were randomized into three groups that received an intracoronary injection of 5 ml of normal saline, 2 mg of nicorandil or 10 µg of alprostadil immediately after measurement of the index of microcirculatory resistance (IMR) and then an intravenous drip containing 5 ml of normal saline, 2 mg of nicorandil or 10 µg of alprostadil once a day for 6 days. The IMR, cardiac function using ultrasound, infarct areas and heparanase levels in infarct areas were measured and compared between the three groups. The IMR decreased markedly 10 min after alprostadil or nicorandil intracoronary injection (both P<0.05) but not following saline injection (P>0.05). After 7 days, the IMR was substantially lower in the alprostadil and nicorandil groups compared with the saline group (both P<0.05) and the ejection fraction was considerably higher in the alprostadil and nicorandil groups compared with the saline group (both P<0.05). Differences in infarct areas and the relative heparanase expression levels among the 3 groups were similar to the differences in the ejection fraction. No significant differences in the above assessment indexes were identified in the alprostadil and nicorandil groups. Alprostadil infusion improved coronary microcirculation function, reduced the infarct area and limited left ventricular dilatation in a pig coronary microvasculature dysfunction model following STEMI.

The ATRIA and Modified-ATRIA Scores in Evaluating the Risk of No-Reflow in Patients With STEMI Undergoing Primary Percutaneous Coronary Intervention

The no-reflow (NR) phenomenon is frequently encountered in acute coronary syndrome. We evaluated the association between anticoagulation and risk factors in atrial fibrillation (ATRIA) and modified ATRIA risk scores and NR in ST-elevation myocardial infarction (STEMI). Consecutive patients (n = 551) who underwent primary percutaneous coronary intervention between December 2019 and June 2020 due to STEMI were included. The mean age of the patients was 60.5 ± 10.8 years (n = 369, 67% male). The ATRIA and modified anticoagulation and risk factors in atrial fibrillation-hyperlipidemia, smoking, male (m-ATRIA-HS) scores were calculated. The NR group had higher frequency of diabetes mellitus (DM), serum creatine kinase-MB (CK-MB) levels, and corrected thrombolysis in myocardial infarction frame count (cTFC) (P = .002, P = .006, and P < .001, respectively). In regression analysis, ATRIA, m-ATRIA-HS, thrombus grade, and cTFC were independent predictors of NR. Age, higher CK-MB, and neutrophil-to-lymphocyte ratio and DM were the other predictors for NR. Pairwise comparison of receiver operating characteristics curve analysis showed that the m-ATRIA-HS (>2, area under curve [AUC]: 0.715) has better performance than ATRIA score (>1, AUC: 0.656), with a P < .022 and z statistics 2.279. In conclusion, ATRIA, especially the m-ATRIA-HS, can be used to evaluate NR risk in STEMI.

Outcomes in Coronary No-Reflow Phenomenon Patients and the Relationship between Kidney Injury Molecule-1 and Coronary No-Reflow Phenomenon

Fundamento

O fenômeno de no-reflow coronário (CNP, do inglês Coronary no-reflow phenomenon) está associado a um risco aumentado de eventos cardiovasculares adversos maiores (ECAM).

Objetivo

Este estudo teve como objetivo avaliar a relação entre os níveis séricos da Molécula-1 de lesão renal (KIM-1) e o CNP em pacientes com infarto agudo do miocárdio com supradesnivelamento do segmento ST (IAMCSST).

Métodos

Este estudo incluiu um total de 160 pacientes (113 homens e 47 mulheres; média de idade: 61,65 ± 12,14 anos) com diagnóstico de IAMCSST. Os pacientes foram divididos em dois grupos, o grupo reflow (GR) (n = 140) e o grupo no-reflow (GNR) (n = 20). Os pacientes foram acompanhados durante um ano. Um valor de p<0,05 foi considerado significativo.

Resultados

O CNP foi observado em 12,50% dos pacientes. O nível de KIM-1 sérico foi significativamente maior no GNR do que no GR (20,26 ± 7,32 vs. 13,45 ± 6,40, p<0,001). O índice de massa corporal (IMC) foi significativamente maior no GNR do que no GR (29,41 (28,48-31,23) vs. 27,56 (25,44-31,03), p=0,047). A frequência cardíaca (FC) foi significativamente menor no GNR do que no GR (61,6 ± 8,04 vs. 80,37 ± 14,61, p<0,001). O escore do European System for Cardiac Operative Risk Evaluation II (EuroSCORE II) foi significativamente maior no GNR do que no GR (3,06 ± 2,22 vs. 2,36 ± 2,85, p=0,016). A incidência de AVC foi significativamente maior no GNR do que no GR (15% vs. 2,90%, p=0,013). O nível basal de KIM-1 (OR = 1,19, IC 95%: 1,07-1,34, p=0,002) e HR (OR = 0,784, IC 95%: 0,69-0,88, p<0,001) foram os preditores independentes de CNP.

Conclusão

Em conclusão, os níveis séricos basais de KIM-1 e a FC mais baixa estão independentemente associados com CNP em pacientes com IAMCSST, e o acidente vascular cerebral foi significativamente maior no GNR em um ano de seguimento. (Arq Bras Cardiol. 2021; 116(2):238-247)

Safety and efficacy of intracoronary sodium nitroprusside for the assessment of coronary fractional flow reserve

Background

Coronary fractional flow reserve (FFR) determination is a valuable tool for the assessment of stenosis significance in intermediate coronary obstructions. Maximal hyperemia is mandatory for this determination. Although intravenous (IV) Adenosine is the standard agent used, its use carries an elevated incidence of side effects. Intracoronary sodium nitroprusside (IC NTP) is a very well-known coronary vasodilator, but it is not routinely used for FFR determinations.

Objectives

The purpose of the present study was to compare FFR determinations and side effect profile of IC NTP with IV Adenosine.

Methods

We prospectively assessed FFR determinations in a total of 20 intermediate coronary artery stenotic lesions in 18 consecutive patients with the administration of IV Adenosine (140 μg/kg/min) and IC NTP (100 μg). The appearance of side effects was registered.

Results

The mean age was 55.5 ± 7.5 years. Fifteen (83%) of the patients were male. Mean FFR values with IC NTP were similar to those obtained with IV Adenosine (0.82 ± 0.07 vs 0.82 ± 0.06, respectively, r = 0.775, p < 0.0001). Intravenous Adenosine induced side effects in 45% of patients (shortness of breath 30%, flushing 5%, headache 5%, angina pectoris 5%, and transient conduction disturbances 10%). No side effects were reported with IC NTP.

Conclusions

IC NTP at a dose of 100 μg is as effective as IV Adenosine for FFR assessment. Besides, it is better tolerated and should be consider as a vasodilator agent in the assessment of FFR.

Protection from Reperfusion Injury with Intracoronary N-Acetylcysteine in Patients with STEMI Undergoing Primary Percutaneous Coronary Intervention in a Cardiac Tertiary Center

BACKGROUND

Evidence suggests that oxidative stress plays a principal role in myocardial damage following ischemia/reperfusion events. Recent studies have shown that the antioxidant properties of N-acetylcysteine (NAC) may have cardioprotective effects in high doses, but-to the best of our knowledge-few studies have assessed this.

OBJECTIVES

Our objective was to investigate the impact of high-dose NAC on ischemia/reperfusion injury.

METHODS

We conducted a randomized double-blind placebo-controlled trial in which 100 consecutive patients with ST-elevation myocardial infarction undergoing percutaneous coronary intervention (PCI) were randomly assigned to the case group (high-dose NAC 100 mg/kg bolus followed by intracoronary NAC 480 mg during PCI then intravenous NAC 10 mg/kg for 12 h) or the control group (5% dextrose). We measured differences in peak creatine kinase-myocardial band (CK-MB) concentration, highly sensitive troponin T (hs-TnT), thrombolysis in myocardial infarction (TIMI) flow, myocardial blush grade (MBG), and corrected thrombolysis in myocardial infarction frame count (cTFC).

RESULTS

The peak CK-MB level was comparable between the two groups (P = 0.327), but patients receiving high-dose NAC demonstrated a significantly larger reduction in hs-TnT (P = 0.02). In total, 94% of the NAC group achieved TIMI flow grade 3 versus 80% of the control group (P = 0.03). No significant differences were observed between the two groups in terms of changes in the cTFC and MBG.

CONCLUSIONS

In this study, NAC improved myocardial reperfusion markers and coronary blood flow, as revealed by differences in peak hs-TnT and TIMI flow grade 3 levels, respectively. Further studies with large samples are warranted to elucidate the role of NAC in this population. ClinicalTrials.gov identifier: NCT01741207, and the Iranian Registry of Clinical Trials (IRCT; http://irct.ir ) registration number: IRCT201301048698N8.

Intracoronary Nicorandil and the Prevention of the No-Reflow Phenomenon During Primary Percutaneous Coronary Intervention in Patients with Acute ST-Segment Elevation Myocardial Infarction

Background

This study aimed to investigate intracoronary nicorandil treatment on the no-reflow phenomenon (NRP) during primary percutaneous coronary intervention (PCI) in patients with acute ST-segment elevation myocardial infarction (STEMI) and to compare nicorandil with sodium nitroprusside.

Material/Methods

Patients with sustained acute STEMI who underwent primary PCI (N=120) were randomly assigned to three groups: the nicorandil-treated group (N=40) had 2 mg of nicorandil injected into the coronary artery at 2 mm beyond the occlusion with balloon pre-dilation; the sodium nitroprusside-treated group (N=40) underwent the same procedure, but with 200 μg of sodium nitroprusside; the control group (N=40) received PCI and balloon pre-dilation only. Coronary angiography, incidence of NRP, hypotensive episodes, ST-segment resolution (STR) rate, levels of N-terminal pro-brain natriuretic peptide (NT-proBNP), creatine kinase-MB (CK-MB), cardiac troponin I (cTnI), wall motion score index (WMSI), and left ventricular ejection fraction (LVEF) were measured before and after primary PCI. Major adverse cardiovascular events (MACEs) post-PCI and at three-month follow-up were recorded.

Results

Patients in the sodium nitroprusside and nicorandil groups had significantly improved thrombolysis in myocardial infarction (TIMI) scores, TIMI myocardial perfusion grade (TMPG), and ST-segment elevation resolution (STR) (P<0.05), and a significantly lower incidence of NRP (P=0.013). The incidence of intraoperative hypotension in the sodium nitroprusside group was significantly greater than the nicorandil and control groups (P=0.035).

Conclusions

Patients with sustained acute STEMI undergoing primary PCI, treated with intracoronary nicorandil had a reduced incidence of the NRP, improved myocardial perfusion and cardiac function.

Current State of the Art in Approaches to Saphenous Vein Graft Interventions

Saphenous vein grafts (SVGs), used during coronary artery bypass graft surgery for severe coronary artery disease, are prone to degeneration and occlusion, leading to poor long-term patency compared with arterial grafts. Interventions used to treat SVG disease are susceptible to high rates of periprocedural MI and no-reflow. To minimise complications seen with these interventions, proper stents, embolic protection devices (EPDs) and pharmacological selection are crucial. Regarding stent selection, evidence has demonstrated superiority of drug-eluting stents over bare-metal stents in SVG intervention. The ACCF/AHA/SCA American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Society for Cardiovascular Angiography and Interventions guidelines recommend the use of EPDs during SVG intervention to decrease the risk of periprocedural MI, distal embolisation and no-reflow. The optimal pharmacological treatment for slow or no-reflow remains unclear, but various vasodilators show promise.

Plasma apelin-12 levels may predict in-hospital major adverse cardiac events in ST-elevation myocardial infarction and the relationship between apelin-12 and the neutrophil/lymphocyte ratio in patients undergoing primary coronary intervention

OBJECTIVE

We aimed to investigate the compliance of plasma apelin-12 levels to show angiographic properties and hospital MACE in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI).

MATERIAL AND METHODS

The association of apelin-12 levels with the N/L ratio on admission was assessed in 170 consecutive patients with primary STEMI undergoing primary PCI. All patient SYNTAX scores and thrombolysis in myocardial infarction (TIMI) flow grades were also assessed. Patients were divided into two groups according to their TIMI flow grade. Patients with a TIMI 0-2 flow and TIMI 3 flow with grade 0/1 myocardial blush grade (MBG) score were defined as the no-reflow group and patients with TIMI grade 3 flow with ⩾2 MBG were considered as the normal flow group.

RESULTS

Baseline apelin-12 levels were significantly lower in the no-reflow group than in the normal flow group (3.3±1.81 vs 6.2±1.74, p<0.001). In-hospital events, including death, myocardial infarction (MI) and re-infarction were significantly higher in patients in the no-reflow group than normal flow group (23% vs 7%, p<0.001). Apelin-12 level was negative correlated with the N/L ratio (r= -0.352, p<0.001), Hs-Crp (r=-0.272, p=0.01) and SYNTAX score (r= -0.246, p=0.029). In the multivariate regression analysis, apelin-12, presence of no-reflow and the SYNTAX score were independent predictors of in-hospital MACE (odds ratio [OR] 1.41, 95% confidence interval (CI) [1.27 to 1.67], p=0.001 for apelin-12, OR 1.085, [0.981 to 1.203], p<0.001 for no-reflow and OR 0.201, 95% CI [0.05 to 0.47], p= 0.004 for SYNTAX score).

CONCLUSION

We have shown that lower apelin-12 level on admission is associated with higher SYNTAX scores and no-reflow phenomenon and may be used as a prognostic marker for hospital MACE in patients with STEMI.

Microvascular Alterations After Temporary Coronary Artery Occlusion: The No-Reflow Phenomenon

In experimental models of temporary coronary artery occlusion, tissue perfusion at the microvascular level remains incomplete even after patency of the infarct-related epicardial coronary artery is established, and distinct perfusion defects develop within the risk zone. This no-reflow phenomenon can be regarded as a basic cardiac response to ischemia-reperfusion. Perfusion defects observed in the clinical realm after reperfusion therapy for myocardial infarction may substantially be related to this mechanism in addition to microembolization and activation of platelets, as suggested in several recent studies. A major determinant of the amount of no-reflow seems to be infarct size itself. Reperfusion-related expansion of noreflow zones occurs within the first hours after the reopening of the coronary artery with a parallel reduction of regional myocardial flow, resulting in a potential therapeutic window. With various cardioprotective interventions, a close correlation between the size of the anatomic no-reflow and necrosis is a reproducible feature, which suggests a causal link between both entities of ischemic cardiac damage. Although vasodilating interventions failed to uncouple no-reflow zones from necrosis, the steps in the causal chain between microvascular and myocardial damage remain to be identified. On a long-term basis, tissue perfusion after ischemia-reperfusion remains markedly compromised for at least 4 weeks. Recent morphometric cardiac analyses suggested that the level of tissue perfusion after 4 weeks is a significant predictor of various indices of infarct healing, such as scar thickness, and infarct expansion index. As a consequence, improving tissue perfusion might concomitantly improve the healing process, which may provide the pathoanatomic basis for prognostic implications of no-reflow.

Early Administration of Intracoronary Nitroprusside Compared with Thrombus Aspiration in Myocardial Perfusion for Acute Myocardial Infarction: A 3-Year Clinical Follow-Up Study

BACKGROUND

Intracoronary nitroprusside and thrombus aspiration have been demonstrated to improve myocardial perfusion during percutaneous coronary interventions (PCI) for ST-segment elevation acute myocardial infarction (STEMI) However, no long-term clinical studies have been performed comparing these approaches.

METHODS

A single medical center retrospective study was conducted to evaluate the effects of intracoronary nitroprusside administration before slow/no-reflow phenomena versus thrombus aspiration during primary PCI. Forty-three consecutive patients with STEMI were enrolled in the intracoronary nitroprusside treatment group. One hundred twenty-four consecutive STEMI patients who received thrombus aspiration were enrolled; ninety-seven consecutive STEMI patients who did not receive either thrombus aspiration or intracoronary nitroprusside treatment were enrolled and served as control subjects. Patients with cardiogenic shock, who had received platelet glycoprotein IIb/IIIa inhibitor, or intra-aortic balloon pump insertion were excluded. Thrombolysis in Myocardial Infarction (TIMI) flow grade, corrected TIMI frame count and TIMI myocardial perfusion grade (TMPG) were assessed prior to and following PCI by two independent cardiologists blinded to the procedures. The rate of major adverse cardiac events (MACE) at 30 days, 1 year, and 3 years after study enrollment as a composite of recurrent myocardial infarction, target-vessel revascularization, and cardiac death were recorded.

RESULTS

The control group had a significantly lower pre-PCI TIMI flow (≤ 1; 49.5% vs. 69.8% vs. 77.4%; p = < 0.001) compared with the nitroprusside and thrombus aspiration groups. The thrombus aspiration group had a significantly higher pre-PCI thrombus score (> 4; 98.4% vs. 88.4% vs. 74.3%; p = < 0.001) and post-PCI TMPG (3; 39.5% vs. 16.3% vs. 20.6%; p = 0.001) compared with the nitroprusside and control groups. No significant differences were noted in the post-PCI thrombus score, 30-day, 1-year and 3-year MACE rate, and Kaplan-Meier curve among 3 groups of patients.

CONCLUSIONS

Although thrombus aspiration provided improved TMPG compared with early administration of intracoronary nitroprusside and neither of both during primary PCI, it did not have a significant impact on 30-day, 1-year and 3-year MACE rate.

KEY WORDS

Acute myocardial infarction; Intracoronary nitroprusside; Thrombus aspiration.

Saphenous Vein Graft Interventions

Saphenous vein graft interventions compose a small but important subset of percutaneous coronary revascularization. Because of their unique biology, percutaneous angioplasty and stenting require tailored patient and lesion selection and modification of intervention technique to optimize outcomes. The use of embolic protection and appropriate adjunctive pharmacology can help minimize periprocedural complications, such as the no-reflow phenomenon. Recommendations for best practice in saphenous vein graft interventions continue to evolve with emerging research and therapy.

Impact of intracoronary adenosine administration during primary PCI: A meta-analysis

BACKGROUND

Aim of the present study was to evaluate all randomized trials, comparing intracoronary adenosine versus placebo in STEMI patients undergoing primary PCI.

METHODS AND RESULTS

PubMed, the Cochrane Library and ISI Web of Knowledge electronic databases were scanned for eligible studies up to February 23rd 2015. The summary measure used was risk ratio (RR) with 95% confidence intervals. A total of 13 studies were eligible, including 1487 patients. Incidence of ST resolution was significantly higher in the IC adenosine group than in the placebo group (RR = 1.20 [1.05–1.38]; p = 0.008). At metaregression, a significant correlation was found between the magnitude of the adenosine-related effect on ST resolution and the mean ischemic time (p = 0.011) or the percentage of patients with the LAD as the infarct-related artery (p = 0.03). Furthermore, we found a larger increase in LVEF (p = 0.02) with a parallel reduction in the incidence of heart failure (HF) (RR = 0.50 [0.28–0.89]; p = 0.02) in the IC adenosine group. Finally, IC adenosine administration was associated with a significantly lower incidence of major adverse cardiac events (MACE) both at short- (RR = 0.62 [0.39–0.98] p = 0.04) and long-term (RR = 0.61 [0.39–0.95] p = 0.03).

CONCLUSIONS

This is the first meta-analysis demonstrating a clinical benefit for IC adenosine in hard endpoints, such as adverse cardiovascular events, in patients undergoing primary PCI.

The "no reflow" phenomenon following acute myocardial infarction: mechanisms and treatment options

If 'no reflow' is observed within 45min of reperfusion using balloon angioplasty or stent, it is probably related to microthromboemboli, which may also contribute to the extension of the 'no reflow' zone by converting 'low reflow' areas into necrotic ones even when reperfusion is achieved more than 45min after the onset of coronary occlusion. Since 'no reflow' is noted when 45min of coronary occlusion has elapsed even in the absence of a thrombus, 'no reflow' late after reperfusion is predominantly due to tissue necrosis and unlikely to be resolved unless methods to reduce infarct size are used. Attempts at reducing the intracoronary thrombus burden during a coronary procedure for acute myocardial infarction (AMI) have been shown to reduce 'no reflow' and improve clinical outcome, as has the use of potent antithrombotic agents. Drugs that can reduce infarct size, when given intracoronary or intravenous in conjunction with a coronary intervention during AMI can also reduce 'no reflow' and improve outcomes in patients with AMI. The prognostic importance of 'no reflow' post-AMI is related to its close correspondence with infarct size. Although several imaging and non-imaging methods have been used to assess 'no reflow' or 'low reflow' myocardial contrast echocardiography remains the ideal method for its assessment both in and outside the cardiac catheterization laboratory.

An update on coronary bypass graft intervention

Coronary artery bypass grafting (CABG) remains one of the most common surgical procedures. In spite of great advancements like arterial grafts and off-pump bypass procedure, recurrent ischaemia may ensue with the lesions of the graft. Early postoperative ischaemia (<30 days) is due to graft occlusion or stenosis, and percutaneous coronary intervention (PCI) is frequently feasible. Late postoperative ischaemia (>3 years) is most often due to a saphenous vein graft (SVG) lesion. Multiple diseased grafts, reduced left ventricular function, and available arterial conduits favour repeat CABG, whereas, a patent left internal mammary artery to left anterior descending favours PCI. Embolic protection reduces atheroembolic myocardial infarction during PCI of SVG and should be routinely used in treatment of SVG lesions. A variety of vasodilators may reduce the risk of or mitigate the consequences of no-reflow. Drug-eluting stents reduce restenosis in SVG grafts, and have become the default strategy for many interventionalists.

Impact of runoff grade after endovascular therapy for femoropopliteal lesions

BACKGROUND

We conceived a new method, runoff grade, to evaluate runoff after endovascular therapy (EVT). We evaluated the validity of using runoff score based on angiographic findings.

METHODS

The subjects were 859 consecutive patients (males, 69%; mean age, 73.0 ± 9.0 years) who underwent EVT for de novo femoropopliteal lesions at Kokura Memorial Hospital. We evaluated the postprocedural tibial runoff, named it runoff grade, classified it into 0 through 2, and retrospectively assessed the relationship with the outcome of EVT. Primary, secondary, and assisted primary patency rates and freedom from major adverse limb events (MALE) were compared between runoff grades.

RESULTS

The mean follow-up period was 31 ± 25 months. The lesion length was 91.5 ± 83.0 mm. The rate of stent use was 52.0%. The primary patency rates at 1, 2, and 3 years were 68.1%, 59.1%, and 53.9%; the secondary patency rates were 90.9%, 88.1%, and 85.9%; the assisted primary patency rates were 79.4%, 72.6%, and 68.5%; and freedom from MALE was 72.5%, 64.8%, and 61.0%, respectively. The primary patency rates at 1, 2, and 3 years were significantly lower in the runoff grade 0 group than in the other groups (55.5% vs 66.7% and 75.6%; 35.8% vs 57.6% and 69.2%; 35.8% vs 53.3% and 60.9% for grade 0, 1, 2, respectively; log-rank, P < .0001). Secondary patency rate (78.5% vs 91.8% and 91.8%; 76.3% vs 88.6% and 89.9%; 72.8% vs 86.3% and 88.2%, respectively; P = .015), assisted primary patency rate (67.0% vs 78.5% and 85.1%; 56.9% vs 71.6% and 79.3%; 47.6% vs 68.0% and 74.8%; respectively, P = .0002), and freedom from MALE (60.8% vs 71.2% and 79.4%; 44.3% vs 64.0% and 72.6%; 36.6% vs 60.7% and 68.5%, respectively; P < .0001) were also similar. After adjustment for age, gender, diabetes, hemodialysis, critical limb ischemia, TransAtlantic Inter-Society Consenus II classification, and stent use, runoff grade was an independent predictor of primary patency.

CONCLUSIONS

Vessels with runoff grade 0 had significantly worse cumulative outcomes. Our results suggested that runoff grade seemed to play an important role to keep the primary patency.

Short-term effect of verapamil on coronary no-reflow associated with percutaneous coronary intervention in patients with acute coronary syndrome: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

To evaluate the clinical efficacy and safety of intracoronary verapamil injection in the prevention and treatment of coronary no-reflow after percutaneous coronary intervention (PCI).

HYPOTHESIS

Intracoronary verapamil injection may be beneficial in preventing no-reflow/slow-flow after PCI.

METHODS

We searched PubMed, Embase, and the Cochrane Central Register of Controlled Trials database. Randomized trials comparing the efficacy and safety of intracoronary verapamil infusion vs control in patients with acute coronary syndrome (ACS) were included. Meta-analysis was performed by RevMan 5.0 software (Cochrane Collaboration, Copenhagen, Denmark) .

RESULTS

Seven trials involving 539 patients were included in the analysis. Verapamil treatment was significantly more effective in decreasing the incidence of no-reflow (risk ratio [RR]: 0.33; 95% confidence interval [CI]: 0.23 to 0.50) as well as reducing the corrected thrombolysis in myocardial infarction (TIMI) frame count (CTFC) (weighted mean difference: -11.62; 95% CI: -16.04 to -7.21) and improving the TIMI myocardial perfusion grade (TMPG) (RR: 0.43; 95% CI: 0.29 to 0.64). Verapamil also reduced the 30-day wall motion index (WMI) compared to the control. Moreover, the procedure reduced the incidence of major adverse cardiac events (MACEs) in ACS patients during hospitalization (RR: 0.37; 95% CI: 0.17 to 0.80) and 2 months after PCI (RR: 0.56; 95% CI: 0.33 to 0.95). However, administration of verapamil did not provide an additional improvement of left ventricular ejection fraction regardless of the time that had passed post-PCI.

CONCLUSIONS

Intracoronary verapamil injection is beneficial in preventing no-reflow/slow-flow, reducing CTFC, improving TMPG, and lowering WMI. It is also likely to reduce the 2-month MACEs in ACS patients post-PCI.

Intracoronary fixed dose of nitroprusside via thrombus aspiration catheter for the prevention of the no-reflow phenomenon following primary percutaneous coronary intervention in acute myocardial infarction

Previous studies have shown that intracoronary (IC) nitroprusside (NTP) injection is a safe and effective strategy for the treatment of no-reflow (NR) during percutaneous coronary intervention (PCI). The present study tested the hypothesis that, on the basis of thrombus aspiration for the treatment of ST-segment elevation myocardial infarction (STEMI), the selective IC administration of a fixed dose of NTP (100 μg) plus tirofiban is a safe and superior treatment method compared with the IC administration of tirofiban alone for the prevention of NR during primary PCI. A total of 162 consecutive patients with STEMI, who underwent primary PCI within 12 h of onset, were randomly assigned to two groups: Group A, IC administration of a fixed dose of NTP (100 μg) plus tirofiban (10 μg/kg) and group B, IC administration of tirofiban (10 μg/kg) alone (n=80 and n=82, respectively). The drugs were selectively injected into the infarct-related artery (IRA) via a thrombus aspiration catheter advanced into the IRA. The primary end-point was post-procedural corrected thrombolysis in myocardial infarction (TIMI) frame count (CTFC). The proportion of complete (>70%) ST-segment resolution (STR); the TIMI myocardial perfusion grade (TMPG) 2–3 ratio following PCI; the peak value of creatine kinase (CK)-MB; the TIMI flow grade; the incidence of major adverse cardiac events (MACEs) and the left ventricular ejection fraction (LVEF) after 6 months of follow-up were observed as the secondary end-points. There were no significant differences in the baseline clinical and angiographic characteristics between the two groups. Compared with group B, group A had i) a lower CTFC (23±7 versus 29±11, P=0.000); ii) a higher proportion of complete STR (72.5 versus 55.9%, P=0.040); iii) an enhanced TMPG 2–3 ratio (71.3 versus 53.7%, P=0.030) and iv) a lower peak CK-MB value (170±56 versus 210±48 U/l, P=0.010). There were no statistically significant differences in the final TIMI grade-3 flow between the two groups (92.5 versus 91.5% for groups A and B, respectively; P=0.956). The LVEF at 6 months was higher in group A than group B (63±9 versus 53±11%, respectively; P=0.001); however, the incidence of MACEs was not statistically different between the two groups, although there was a trend indicating improvement in group A (log rank χ²=0.953, P=0.489). The selective IC administration of a fixed dose of NTP (100 μg) plus tirofiban via a thrombus aspiration catheter advanced into the IRA is a safe and superior treatment method compared with tirofiban alone in patients with STEMI undergoing primary PCI. This novel therapeutic strategy improves the myocardial level perfusion, in addition to reducing the infarct size. Furthermore, it may improve the postoperative clinical prognosis following PCI.

Treating and preventing no reflow in the cardiac catheterization laboratory

The no reflow phenomenon can happen during elective or primary percutaneous coronary intervention. This phenomenon is thought to be a complex process involving multiple factors that eventually lead to microvascular obstruction and endothelial disruption. Key pathogenic components include distal atherothrombotic embolization, ischemic injury, reperfusion injury, and susceptibility of coronary microcirculation to injury. Thus, pharmacologic and mechanical strategies to prevent and treat no reflow target these mechanisms. Specifically, pharmacologic therapy consisting of vasodilators and antiplatelet agents have shown benefit in the treatment of no-reflow and mechanical therapies such as distal protection and aspiration thrombectomy have also shown benefit.

Complications of coronary intervention: device embolisation, no-reflow, air embolism

The introduction of drug-eluting stents, better equipment, stronger antiplatelet drugs, and higher levels of operator experience has led to markedly improved patency rates for complex percutaneous coronary interventions (PCIs). The evolving techniques of contemporary PCI have been unable to completely eliminate complications. However, rigorous preventive measures pre-empt the appearance of complications. During traversal of severely diseased coronary arteries and manipulating equipment, particularly devices with detachable components, the opportunity for loss or embolisation of material in the coronary circulation presents itself. Device embolisation is associated with periprocedural myocardial infarction and emergent referral to surgery, particularly if the device is not retrieved. The coronary no-reflow phenomenon is a feared complication of PCI. It is associated with a worse prognosis and has been shown to be an independent predictor of death, myocardial infarction and impaired left ventricular function. Air embolism can be prevented by flushing of catheters during equipment exchanges.

Pharmacotherapy During Saphenous Vein Graft Intervention

Coronary revascularization using saphenous vein grafts is an important treatment modality for patients with severe coronary artery disease. Percutaneous intervention of these grafts is often the best option for patients who develop severe stenosis of the vein grafts. Use of adjunctive glycoprotein IIb/IIIa inhibitors does not confer added benefit with ischemic endpoints as compared with heparin alone, but it increases the risk of bleeding. Bivalirudin used as the primary anticoagulant lowers the risk of bleeding. No-reflow frequently complicates vein graft interventions but can be treated with vasoactive agents such as calcium channel blockers, adenosine, and nitroprusside.

Ischemic post-conditioning and vasodilator therapy during standard cardiopulmonary resuscitation to reduce cardiac and brain injury after prolonged untreated ventricular fibrillation

AIM OF THE STUDY

We investigated the effects of ischemic postconditioning (IPC) with and without cardioprotective vasodilatory therapy (CVT) at the initiation of cardiopulmonary resuscitation (CPR) on cardio-cerebral function and 48-h survival.

METHODS

Prospective randomized animal study. Following 15 min of ventricular fibrillation, 42 Yorkshire farm pigs weighing an average of 34 ± 2 kg were randomized to receive standard CPR (SCPR, n=12), SCPR+IPC (n=10), SCPR+IPC+CVT (n=10), or SCPR+CVT (n=10). IPC was delivered during the first 3 min of CPR with 4 cycles of 20s of chest compressions followed by 20-s pauses. CVT consisted of intravenous sodium nitroprusside (2mg) and adenosine (24 mg) during the first minute of CPR. Epinephrine was given in all groups per standard protocol. A transthoracic echocardiogram was obtained on all survivors 1 and 4h post-ROSC. The brains were extracted after euthanasia at least 24h later to assess ischemic injury in 7 regions. Ischemic injury was graded on a 0-4 scale with (0=no injury to 4 ≥ 50% neural injury). The sum of the regional scores was reported as cerebral histological score (CHS). 48 h survival was reported.

RESULTS

Post-resuscitation left ventricular ejection (LVEF) fraction improved in SCPR+CVT, SCPR+IPC+CVT and SCPR+IPC groups compared to SCPR (59% ± 9%, 52% ± 14%, 52% ± 14% vs. 35% ± 11%, respectively, p<0.05). Only SCPR+IPC and SCPR+IPC+CVT, but not SCPR+CVT, had lower mean CHS compared to SCPR (5.8 ± 2.6, 2.8 ± 1.8 vs. 10 ± 2.1, respectively, p<0.01). The 48-h survival among SCPR+IPC, SCPR+CVT, SCPR+IPC+CVT and SCPR was 6/10, 3/10, 5/10 and 1/12, respectively (Cox regression p<0.01).

CONCLUSIONS

IPC and CVT during standard CPR improved post-resuscitation LVEF but only IPC was independently neuroprotective and improved 48-h survival after 15 min of untreated cardiac arrest in pigs.

Comparison of efficacy and safety of intracoronary sodium nitroprusside and intravenous adenosine for assessing fractional flow reserve

OBJECTIVES

The purpose of this study was to compare the efficacy and safety of intracoronary (IC) nitroprusside and intravenous adenosine (IVA) for assessing fractional flow reserve (FFR).

BACKGROUND

IV infusion of adenosine is a standard method to achieve a coronary hyperemia for FFR measurement. However, adenosine is expensive, causes multiple side effects, and is contraindicated in patients with reactive airway disease. Sodium nitroprusside (NTP) is a strong coronary vasodilator but its efficacy and safety for assessing FFR is not well established.

METHODS

We compared FFR response and side effects profile of IC NTP and IVA. Bolus of NTP at a dose of 100 μg and IVA (140 μg/kg/min) were used to achieve coronary hyperemia.

RESULTS

We evaluated 75 lesions in 53 patients (60% male) mean age 61.6 ± 13.9 years. Mean FFR after NTP was similar to FFR after adenosine (0.836 ± 0.107 vs. 0.856 ± 0.106; P = 0.26; r = 0.91, P < 0.001). NTP induced maximal stable hyperemia within 10 sec (mean: 6.4 ± 1) which lasted consistently between 38 and 60 sec (mean 51 ± 7.5). NTP caused significant (14%), but asymptomatic decrease in mean blood pressure which returned to baseline within 60 sec. Adenosine caused shortness of breath in 26%, headache and flushing in 19%, and transient second degree heart block in 6% of patients. No adverse symptoms were reported after NTP.

CONCLUSIONS

IC NTP is as effective as IVA for measuring FFR. NTP is better tolerated by patients. Since NTP is inexpensive, readily available, well tolerated, and safe, it may be a better choice for FFR assessment.

REstoration of COronary flow in patients with no-reflow after primary coronary interVEntion of acute myocaRdial infarction (RECOVER)

BACKGROUND

No randomized trial has been conducted to compare different vasodilators for treating no-reflow during primary percutaneous coronary intervention (PCI) for ST-segment elevation acute myocardial infarction.

METHODS

The prospective, randomized, 2-center trial was designed to compare the effect of 3 different vasodilators on coronary no-reflow. A total of 102 patients with no-reflow in primary PCI were randomized to receive intracoronary infusion of diltiazem, verapamil, or nitroglycerin (n = 34 in each group) through selective microcatheter. The primary end point was coronary flow improvement in corrected thrombolysis in myocardial infarction frame count (CTFC) after administration of the drug.

RESULTS

Compared with that of the nitroglycerin group, there was a significant improvement of CTFC after drug infusion in the diltiazem and verapamil groups (42.4 frames vs 28.1 and 28.4 frames, P < .001). The improvement in CTFC was similar between the diltiazem and verapamil groups (P = .9). Compared with the nitroglycerin group, the diltiazem and verapamil groups had more complete ST-segment resolution at 3 hours after PCI, lower peak troponin T level, and lower N-terminal pro-B-type natriuretic peptide levels at 1 and 30 days after PCI. After drug infusion, the drop of heart rate and systolic blood pressure in the verapamil group was greater than that in the diltiazem and nitroglycerin groups.

CONCLUSION

Intracoronary infusion of diltiazem or verapamil can reverse no-reflow more effectively than nitroglycerin during primary PCI for acute myocardial infarction. The efficacy of diltiazem and verapamil is similar, and diltiazem seems safer.

A survival case of cardiogenic shock due to left main coronary artery myocardial infarction: successful cooperation with on-site percutaneous coronary intervention and helicopter emergency medical service

A 54-year-old man was referred to a local hospital, located about 90 km from our hospital, with cardiogenic shock due to left main coronary artery infarction (LMCA-MI). Percutaneous coronary intervention (PCI) was performed under intra-aortic balloon pumping (IABP) support, but resulted in insufficient reperfusion and his condition worsened. The helicopter emergency medical service (HEMS) rapidly transported the patient to our hospital. After percutaneous cardio-pulmonary support system (PCPS) insertion, PCI could establish the coronary flow. A series of intensive therapies saved the patient. The cooperation of medical and emergency service system following revascularization and intensive care saved the patient with LMCA-MI accompanied by cardiogenic shock.

Acute effect of sodium nitroprusside on microvascular dysfunction in patients who underwent percutaneous coronary intervention for acute ST-segment elevation myocardial infarction

Even in the era of thrombus aspiration and distal protection for ST-segment elevation acute myocardial infarction (STEMI), microvascular dysfunction does exist and improvement of microvascular dysfunction can improve the prognosis and/or left ventricular dysfunction. We evaluated the acute effects of nitroprusside (NTP) on coronary microvascular injury that occurred after primary percutaneous coronary intervention (PCI) for STEMI in 18 patients. The final Thrombolysis in Myocardial Infarction trial (TIMI) flow grade after PCI was 3 in 17 patients and 2 in 1 patient. The index of microcirculatory resistance (IMR) was improved significantly from 76 ± 42 to 45 ± 37 (P = 0.0006) by intracoronary NTP administration. IMR improved to the normal range (IMR < 30) in 9 patients (50%). Higher TIMI flow grade and lower IMR at baseline were observed more frequently in patients whose IMR recovered to normal range after NTP administration. NTP improved the microcirculatory dysfunction at the acute phase in patients who underwent PCI for STEMI and had final TIMI 3 flow in almost all cases.

The management of thrombotic lesions in the cardiac catheterization laboratory

Plaque rupture with superimposed thrombosis is the major mechanism of acute coronary syndromes. Although angiography underestimates the presence of thrombi, their detection is a poor prognostic indicator which is proportional to their size. Although emergent percutaneous coronary intervention (PCI) in the setting of ST elevation myocardial infarction (STEMI) and early PCI in the setting of unstable angina and non-STEMI were shown to be preferred strategies, the presence of angiographic thrombosis by virtue of causing micro and macro embolization can reduce the benefit of the intervention. Antiplatelet therapy especially using glycoprotein IIb/IIIa inhibitors reduces thrombus size, and improves myocardial perfusion and ventricular function. Routine manual aspiration prior to PCI in STEMI also improves myocardial flow and reduces distal embolization and improves survival. Distal embolic protection devices and mechanical thrombectomy do not have the same clinical benefits however, rheolytic thrombectomy may have a role in large vessels with a large thrombi.

Peri-interventional coronary vasomotion

A percutaneous coronary intervention (PCI) is a unique condition to study the effects of ischemia and reperfusion in patients with severe coronary atherosclerosis when coronary vasomotor function is compromised by loss of endothelial and autoregulatory vasodilation. We studied the effects of intracoronary non-selective α-, as well as selective α(1)- and α(2)-blockade in counteracting the observed vasoconstriction in patients with stable and unstable angina and in patients with acute myocardial infarction. Coronary vasoconstriction in our studies was a diffuse phenomenon and involved not only the culprit lesion but also vessels with angiographically not visible plaques. Post-PCI vasoconstriction was reflected by increased coronary vascular resistance and associated with decreased LV-function. α (1)-Blockade with urapidil dilated epicardial coronary arteries, improved coronary flow reserve and counteracted LV dysfunction. Non-selective α-blockade with phentolamine induced epicardial and microvascular dilation, while selective α(2)-blockade with yohimbine had only minor vasodilator and functional effects. Intracoronary α-blockade also attenuated the no-reflow phenomenon following primary PCI. This article is part of a Special Issue entitled "Coronary Blood Flow".

Saphenous vein graft intervention

Saphenous vein grafts are commonly used conduits for surgical revascularization of coronary arteries but are associated with poor long-term patency rates. Percutaneous revascularization of saphenous vein grafts is associated with worse clinical outcomes including higher rates of in-stent restenosis, target vessel revascularization, myocardial infarction, and death compared with percutaneous coronary intervention of native coronary arteries. Use of embolic protection devices is a Class I indication according to the American College of Cardiology/American Heart Association guidelines to decrease the risk of distal embolization, no-reflow, and periprocedural myocardial infarction. Nonetheless, these devices are underused in clinical practice. Various pharmacological agents are available that may also reduce the risk of or mitigate the consequences of no-reflow. Covered stents do not decrease the rates of periprocedural myocardial infarction and restenosis. Most available evidence supports treatment with drug-eluting stents in this high-risk lesion subset to reduce angiographic and clinical restenosis, although large, randomized trials comparing drug-eluting stents and bare-metal stents are needed.

Management of the no-reflow phenomenon

The lack of reperfusion of myocardium after prolonged ischaemia that may occur despite opening of the infarct-related artery is termed "no reflow". No reflow or slow flow occurs in 3-4% of all percutaneous coronary interventions, and is most common after emergency revascularization for acute myocardial infarction. In this setting no reflow is reported to occur in 30% to 40% of interventions when defined by myocardial perfusion techniques such as myocardial contrast echocardiography. No reflow is clinically important as it is independently associated with increased occurrence of malignant arrhythmias, cardiac failure, as well as in-hospital and long-term mortality. Previously the no-reflow phenomenon has been difficult to treat effectively, but recent advances in the understanding of the pathophysiology of no reflow have led to several novel treatment strategies. These include prophylactic use of vasodilator therapies, mechanical devices, ischaemic postconditioning and potent platelet inhibitors. As no reflow is a multifactorial process, a combination of these treatments is more likely to be effective than any of these alone. In this review we discuss the pathophysiology of no reflow and present the numerous recent advances in therapy for this important clinical problem.

Stenting of complex lesions: an overview

Contemporary management of coronary artery disease relies increasingly on percutaneous techniques combined with medical therapy. Although percutaneous coronary intervention (PCI) can be performed successfully in most lesions, several difficult lesion subsets continue to present unique technical challenges. These complex lesions may be classified according to anatomic criteria, including extensive calcification, thrombus, and chronic occlusions, or by location, such as bifurcations, saphenous vein grafts and unprotected left main. PCI of these lesions often requires novel devices, such as drug-eluting stents, hydrophilic guidewires, distal protection balloons or filters, thrombectomy catheters, rotational atherectomy, and cutting balloons. An integrated approach that combines these devices with specialized techniques and adjunctive pharmacologic agents has greatly improved PCI success rates for these complex lesions.

Unanticipated signaling events associated with cardiac adenylyl cyclase gene transfer

The published papers on the effects of increased cardiac expression of adenylyl cyclase type 6 (AC6) are reviewed. These include the effects of AC on normal and failing left ventricle in several pathophysiological models in mice and pigs. In addition, the effects of increased expression of AC6 in cultured neonatal and adult rat cardiac myocytes are discussed in the context of attempting to establish mechanisms for the unanticipated beneficial effects of AC6 on the failing heart. This article is part of a Special Section entitled "Special Section: Cardiovascular Gene Therapy".