Effects of diltiazem on perioperative ischemia, arrhythmias, and myocardial function in patients undergoing elective coronary bypass grafting

Prevention of Atrial Fibrillation After Cardiac Surgery: A Review of Literature and Comparison of Different Treatment Modalities

Atrial fibrillation is the most common arrhythmia to occur after cardiac surgery, with an incidence of 10% to 50%. It is associated with postoperative complications including increased risk of stroke, prolonged hospital stays and increased costs. Despite new insights into the mechanisms of atrial fibrillation, no specific etiologic factor has been identified as the sole perpetrator of the arrhythmia. Current evidence suggests that the pathophysiology of atrial fibrillation in general, as well as after cardiac surgery, is multifactorial. Studies have also shown that new-onset postoperative atrial fibrillation following cardiac surgery is associated with a higher risk of short-term and long-term mortality. Furthermore, it has been demonstrated that prophylactic medical therapy decreases the incidence of postoperative atrial fibrillation after cardiac surgery. Of note, the incidence of postoperative atrial fibrillation has not changed during the last decades despite the numerous preventive strategies and operative techniques proposed, although the perioperative and postoperative care of cardiac patients as such has improved.

Perioperative diltiazem therapy was not associated with improved perioperative and long-term outcomes in patients undergoing on-pump coronary artery bypass grafting

Background

Diltiazem has been used during the perioperative period in patients undergoing coronary artery bypass grafting (CABG) to prevent arterial graft spasm. However, its long-term outcome effects remain unclear.

Methods

Patient records obtained from the Society of Thoracic Surgeons and the Geisinger Clinic electronic health records between October 2008 and October 2018 were screened. Adult patients who had isolated CABG with cardiopulmonary bypass were included. Cohorts of patients who received diltiazem (DILT) and those who did not (non-DILT) were matched by propensity scores based on age, gender, surgical year, Society of Thoracic Surgeons mortality and morbidity scores, and number of arterial grafts. Incidence rate ratios (IRRs) were estimated for DILT vs non-DILT on short-term adverse outcomes. Long-term survival over time was compared between DILT vs non-DILT using Kaplan-Meier curves.

Results

Among the 1004 patients included in the analyses, IRRs for the DILT group relative to the non-DILT group were: 30-day all-cause mortality, IRR: 2.33, 95% confidence interval (CI): 0.91-5.96, P=0.07; postoperative myocardial ischaemia, IRR: 1.10, 95% CI: 0.60-2.02, P=0.75; new onset atrial fibrillation, IRR: 1.06, 95% CI: 0.78-1.43, P=0.73; stroke/transient ischaemic attack, IRR: 0.76, 95% CI: 0.17-3.38, P=0.71. For long-term survival, Kaplan-Meier curves stratified by diltiazem revealed no differences in survival rates between DILT and non-DILT groups.

Conclusion

For patients undergoing on-pump CABG, perioperative diltiazem therapy did not show significant short- or long-term outcome advantages over those who did not receive diltiazem.

Diazepam ameliorated myocardial ischemia-reperfusion injury via inhibition of C-C chemokine receptor type 2/Tumor necrosis factor-alpha/Interleukins and Bcl-2-associated X protein/Caspase-3 pathways in experimental rats

Myocardial ischemia-reperfusion injury (IRI) is one of the most leading concerns for public health globally. Diazepam, a local anesthetic, has been reported for its cardioprotective potential. The present investigation aimed to evaluate the possible mechanism of action of diazepam against left anterior descending ligation-induced myocardial IRI in experimental rats. IRI was induced in healthy male rats by ligating coronary artery for 30 min and then reperfused for 60 min. The animals were pre-treated with either vehicle or diltiazem (10 mg/kg) or diazepam (1, 2.5, and 5 mg/kg) for 14 days. Compared to the IRI group, diazepam (2.5 and 5 mg/kg) markedly (P<0.05) attenuated IRI-induced alterations in cardiac function and oxido-nitrosative stress. In addition, diazepam prominently (P<0.05) improved cardiac Na⁺K⁺ATPase, Ca²⁺ATPase levels and hypoxia-inducible factor-1 alpha (HIF-1α) mRNA expression. It also significantly (P<0.05) down-regulated cardiac mRNA expressions of cardiac troponin I (cTn-I), C-C chemokine receptor type 2 (CCR2), tumor necrosis factor-alpha (TNF-α), interleukins (IL)-1β, and IL-6. In western blot analysis, IRI-induced myocardial apoptosis was reduced by diazepam treatment reflected by a marked (P<0.05) decreased in Bcl-2-associated X protein (Bax) and Caspase-3 protein expression. Diazepam also efficiently (P<0.05) improved IRI-induced histological aberration in cardiac tissue. In conclusion, diazepam exerts cardioprotective effect by inhibiting inflammatory release (CCR2, TNF-α, and ILs), oxido-nitrosative stress, and apoptosis (Bax and Caspase-3) pathway during myocardial IRI in experimental rats.

Perioperative diltiazem or nitroglycerin in on-pump coronary artery bypass: A systematic review and network meta-analysis

Background

Arterial graft spasm is a severe complication after coronary artery bypass graft (CABG). Among numerous potential antispasmodic agents, systemic application of diltiazem and nitroglycerin had been investigated most frequently over the past three decades. However, it remains inconclusive if either or both agents could improve patient outcomes by preventing graft spasm when applied perioperatively, and, if so, which one would be a better choice. The current systematic review and network meta-analysis aims to summarize the data from all available randomized clinical trials of perioperative continuous intravenous infusion of diltiazem and/or nitroglycerin in patients undergoing on-pump CABG in order to define and compare their roles in graft spasm prevention and their impacts on perioperative outcomes.

Methods

We searched Ovid Medline, PubMed, CINAHL, Google Scholar and Cochrane Center for randomized controlled trials that reported outcome effects of perioperative continuous intravenous infusion of diltiazem and/or nitroglycerin in patients undergoing elective on-pump CABG. Conventional meta-analyses were conducted to evaluate the pairwise comparisons (diltiazem vs. placebo; nitroglycerin vs. placebo; diltiazem vs. nitroglycerin) on perioperative outcomes. Network meta-analyses were implemented to compare the three regimens through direct and indirect comparison.

Results

Twenty-seven studies involving 1,660 patients were included. Pairwise and network meta-analyses found no significant difference in mortality among the groups. There are four studies that reported blood flow measurements of internal mammary artery grafts intraoperatively after dissecting or immediately after distal anastomosis while patients were on continuous intravenous infusion of diltiazem and nitroglycerin. Although insufficient for data synthesis, the measured results from all four studies suggest that both diltiazem and nitroglycerin significantly increased blood flow of arterial grafts compared to placebo. For other perioperative outcomes, compared to diltiazem, patients that received nitroglycerin had higher odds of postoperative atrial fibrillation (OR = 2.67, 95% CI: 1.15 to 6.24) and higher peak serum cardiac enzymes. Patients that received placebo had higher odds of atrial fibrillation (OR = 3.00, 95% CI: 1.18 to 7.63) and lower odds of requiring inotrope support (OR = 0.19, 95% CI: 0.04 to 0.73) compared to diltiazem. Data from the network meta-analysis indicated that diltiazem had significantly lower odds of postoperative atrial fibrillation compared to nitroglycerin (OR = 0.39, 95% CI: 0.18 to 0.85). In fact, the rank from highest to lowest rates of postoperative atrial fibrillation was placebo>nitroglycerin>diltiazem. The rank from highest to lowest odds of requiring inotropic support is nitroglycerin> diltiazem>placebo. However, placebo had significantly higher odds of postoperative myocardial infarction than diltiazem (OR = 4.51, 95% CI: 1.34 to 15.25). The rank from highest to lowest odds of postoperative myocardial infarction, transient cardiac ischemic event and atrial fibrillation is placebo>nitroglycerin>diltiazem.

Conclusion

Compared to nitroglycerin and placebo, perioperative continuous intravenous infusion of diltiazem had stronger protective effects against postoperative ischemic cardiac injuries and atrial fibrillation although patients may need more inotropic support. The increased blood flow from diltiazem use in arterial grafts may potentially contribute to the drug’s outcome benefits.

Perspectives and challenges of antioxidant therapy for atrial fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia associated with significant morbidity and mortality. The mechanisms underlying the pathogenesis of AF are poorly understood, although electrophysiological remodeling has been described as an important initiating step. There is growing evidence that oxidative stress is involved in the pathogenesis of AF. Many known triggers of oxidative stress, such as age, diabetes, smoking, and inflammation, are linked with an increased risk of arrhythmia. Numerous preclinical studies and clinical trials reported the importance of antioxidant therapy in the prevention of AF, using vitamins C and E, polyunsaturated fatty acids, statins, or nitric oxide donors. The aim of our work is to give a current overview and analysis of opportunities, challenges, and benefits of antioxidant therapy in AF.

Effect of ColchiciNe on the InciDence of Atrial Fibrillation in Open Heart Surgery Patients: END-AF Trial

BACKGROUND

Atrial fibrillation (AF) is a common arrhythmia in patients undergoing cardiac surgery and may result in significant morbidity and increased hospital stay. This study was conducted to determine if colchicine administered preoperatively to patients undergoing cardiac surgery and continued during hospitalization is effective in reducing the incidence of postoperative AF.

METHODS

In this multicenter prospective randomized open-label study, consecutive patients with no history of AF and scheduled to undergo elective cardiac surgery (n = 360) were randomized to colchicine (n = 179) or no-colchicine (n = 181). Main exclusion criteria were history of AF or supraventricular arrhythmias or absence of sinus rhythm at enrolment, and contraindications to colchicine. Colchicine was orally administered 12 to 24 hours preoperatively and continued until hospital discharge. The primary efficacy end point was documented AF lasting more than 5 minutes. Safety end point was colchicine adverse effects.

RESULTS

In-hospital mortality was 3.3%. The primary end point of AF occurred in 63 patients (17.5%): 26 (14.5%) in the colchicine group and 37 (20.5%) in the no-colchicine group (relative risk reduction 29.3% [P = .14]). Diarrhea occurred in 54 patients, 44 (24.6%) on colchicine and 10 (5.5%) on no-colchicine (P < .001). Diarrhea led to discontinuation of colchicine in 23 (52%) of the 44 patients.

CONCLUSION

Colchicine administered preoperatively to patients undergoing cardiac surgery and continued until hospital discharge failed to significantly reduce the incidence of early postoperative AF. Diarrhea was the most common adverse effect of colchicine leading to its discontinuation in more than half of the patients with this adverse effect.

Diltiazem versus Amiodarone to Prevent Atrial Fibrillation in Coronary Surgery

The prophylactic effect of amiodarone on atrial fibrillation after coronary bypass grafting with extracorporeal circulation was compared with that of diltiazem in two groups of 60 patients each. Patients were monitored continuously for 8 days. The incidence of atrial fibrillation was recorded retrospectively in a control group of 60 patients who received our standard prophylactic regimen of an oral beta blocker. The incidence of postoperative atrial fibrillation was not significantly different in the two test groups: 11.7% for the amiodarone group and 10% for the diltiazem group. The incidence of atrial fibrillation in the control group was 23.3% and the differences were marginally significant when compared to the amiodarone ( p = 0.093) and diltiazem groups ( p = 0.050). The prophylactic use of diltiazem or amiodarone is feasible and safe for patients undergoing coronary bypass, with similar rates of atrial fibrillation.

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.

Left ventricular diastolic dysfunction of the cardiac surgery patient; a point of view for the cardiac surgeon and cardio-anesthesiologist

BACKGROUND

Left ventricular diastolic dysfunction (DD) is defined as the inability of the ventricle to fill to a normal end-diastolic volume, both during exercise as well as at rest, while left atrial pressure does not exceed 12 mm Hg. We examined the concept of left ventricular diastolic dysfunction in a cardiac surgery setting.

MATERIALS AND METHODS

Literature review was carried out in order to identify the overall experience of an important and highly underestimated issue: the unexpected adverse outcome due to ventricular stiffness, following cardiac surgery.

RESULTS

Although diverse group of patients for cardiac surgery could potentially affected from diastolic dysfunction, there are only few studies looking in to the impact of DD on the postoperative outcome; Trans-thoracic echo-cardiography (TTE) is the main stay for the diagnosis of DD. Intraoperative trans-oesophageal (TOE) adds to the management. Subgroups of DD can be defined with prognostic significance.

CONCLUSION

DD with elevated left ventricular end-diastolic pressure can predispose to increased perioperative mortality and morbidity. Furthermore, DD is often associated with systolic dysfunction, left ventricular hypertrophy or indeed pulmonary hypertension. When the diagnosis of DD is made, peri-operative attention to this group of patients becomes mandatory.

Acute ischemic syndromes following coronary artery bypass graft surgery

Coronary artery bypass graft (CABG) surgery, performed for the control of angina pectoris, leads to postoperative relief from symptoms in most patients. Amelioration of ischemia and improvement in exercise capacity after CABG are well documented. However, patients currently undergoing CABG are more complex than in the past--they are older and are maintained on medical therapy for longer periods. A large number of these patients have had one or more previous myocardial revascularization procedures. The post-operative period would appear to be a time of vulnerability for coronary events. However, previous investigators have focused on the pre- and intraoperative aspects of peri-CABG ischemia. Outcome data suggest that the postoperative interval is at least equally important as a determinant of short- and long-term morbidity and mortality. We discuss the epidemiology, etiology, pathophysiology, and treatment of ischemic syndromes in the postoperative period after CABG. In addition, we review recent data from a series of 14 patients, observed at our institution, who underwent cardiac catheterization and, in some cases, angioplasty of the culprit vessel in the immediate postoperative period.

Effect of verapamil on tachycardia-induced early cellular electrical remodeling in rabbit atrium

We investigated the effects of a 7-day verapamil pretreatment (VPT, 7.5 mg/kg bodyweight subcutaneously every 12 h) on ionic currents and molecular mechanisms underlying tachycardia-induced early electrical remodeling after 24-h rapid atrial pacing (RAP, 600 bpm) in rabbit atrium. Animals were divided into four groups (n = 6 each group): control (not paced, no verapamil), paced only, verapamil only and verapamil and paced, respectively. VPT doubled ICa,L [7.0 +/- 0.7 pA/pF (control) vs 14.2 +/- 0.6 pA/pF (verapamil only)]. RAP reduced ICa,L by 48% to 3.6 +/- 0.7 pA/pF (paced only). RAP did not affect ICa,L in verapamil-treated animals and averaged 15.3 +/- 0.2 pA/pF (paced and verapamil). RAP resulted in a significant decrease of the expression of the alpha1c subunit (-24.7%) and the beta2A subunit (-13.3%), respectively. VPT led to a similar alteration of subunit expression as RAP ["control" vs "verapamil only", decrease of alpha1c subunit (-25.4%), but no significant change in beta2A subunit expression]. However, after VPT, further diminishment of alpha1c and beta2A subunit expression after rapid atrial pacing was absent. ("verapamil" vs "verapamil and paced", n = 6 both groups). RAP decreased Ito [-45%, 51.5 +/- 3.9 pA/pF (control) vs 26.8 +/- 1.5 pA/pF (paced only)] and was not influenceable by VPT. IK1 was neither affected by RAP nor verapamil pretreatment. Downregulation of alpha1c and beta2A subunit expression and the resulting decay of ICa,L current densities were prevented by verapamil. However, these effects are abolished by multiple other adverse effects of verapamil on atrial electrophysiology.

Prevention of atrial fibrillation after cardiac surgery

Atrial fibrillation is the most common arrhythmia occurring after heart surgery. Its prevalence after coronary artery bypass surgery is 17-33%. Atrial fibrillation requires additional treatment, lengthens hospitalization and increases the overall expenses of cardiac surgery. Atrial fibrillation can cause hemodynamic problems, predispose to congestive heart failure and increase the risk of stroke. Beta-blockers have been shown to effectively prevent atrial fibrillation, and beta-blockers should be a part of the medication of every patient undergoing cardiac surgery, if there are no contraindications. Amiodarone therapy can also be considered for especially high-risk patients.

Nitric oxide homeostasis as a target for drug additives to cardioplegia

The vascular endothelium of the coronary arteries has been identified as the important organ that locally regulates coronary perfusion and cardiac function by paracrine secretion of nitric oxide (NO) and vasoactive peptides. NO is constitutively produced in endothelial cells by endothelial nitric oxide synthase (eNOS). NO derived from this enzyme exerts important biological functions including vasodilatation, scavenging of superoxide and inhibition of platelet aggregation. Routine cardiac surgery or cardiologic interventions lead to a serious temporary or persistent disturbance in NO homeostasis. The clinical consequences are "endothelial dysfunction", leading to "myocardial dysfunction": no- or low-reflow phenomenon and temporary reduction of myocardial pump function. Uncoupling of eNOS (one electron transfer to molecular oxygen, the second substrate of eNOS) during ischemia-reperfusion due to diminished availability of L-arginine and/or tetrahydrobiopterin is even discussed as one major source of superoxide formation. Therefore maintenance of normal NO homeostasis seems to be an important factor protecting from ischemia/reperfusion (I/R) injury. Both, the clinical situations of cardioplegic arrest as well as hypothermic cardioplegic storage are followed by reperfusion. However, the presently used cardioplegic solutions to arrest and/or store the heart, thereby reducing myocardial oxygen consumption and metabolism, are designed to preserve myocytes mainly and not endothelial cells. This review will focus on possible drug additives to cardioplegia, which may help to maintain normal NO homeostasis after I/R.

Prophylactic therapy to prevent atrial arrhythmia after cardiac surgery

PURPOSE OF REVIEW

Atrial fibrillation after cardiac surgery is associated with adverse outcomes and increased costs. Accordingly, therapy should be provided to prevent postoperative atrial fibrillation. The evaluation of therapies to do so is an area of active investigation with significant recent advances. The purpose of this review is to summarize these recent advances in the context of our previous knowledge base regarding the prevention of postoperative atrial fibrillation.

RECENT FINDINGS

Recent evaluations of therapy to prevent postoperative atrial fibrillation have raised the prominence of prophylactic amiodarone, redefined the efficacy of prophylactic standard beta-blockers in contemporary cardiac surgical populations, provided further evidence for the use of prophylactic sotalol, magnesium, and atrial pacing, and identified new approaches, including the use of combination therapy, for the prevention of postoperative atrial fibrillation.

SUMMARY

According to newly released ACC/AHA/ESC guidelines, use of standard beta-blockers or amiodarone to prevent postoperative atrial fibrillation have a level of evidence of A. Use of prophylactic sotalol has a level of evidence of B, while the use of prophylactic intravenous magnesium or atrial pacing has a lower level of evidence. The use of novel and combination therapies continues to be an area of active investigation.

Pharmacologic Prophylaxis

New-onset atrial fibrillation (AF) occurs frequently in patients after cardiac surgery. The purpose of this study was to review the published trials and to provide clinical practice guidelines for pharmacologic prophylaxis against postoperative AF. Trials of pharmacologic prophylaxis against AF after heart surgery were identified by searching MEDLINE, the Cochrane Controlled Trials Register, and the bibliographies of published reports. Evidence grades and clinical recommendation scores were assigned to each prophylactic drug based on published evidence. Ninety-one trials were identified. The primary study design was a randomized, controlled trial of one drug vs placebo/usual care. Pharmacologic therapies that are reviewed include Vaughan-Williams class II agents (ie, beta-receptor antagonists) [29 trials; 2,901 patients], Vaughan-Williams class III agents (ie, sotalol and amiodarone) [18 trials; 2,978 patients], Vaughan-Williams class IV agents (ie, verapamil and diltiazem) [5 trials; 601 patients], and Vaughan-Williams class I agents (ie, quinidine and procainamide) [3 trials; 246 patients], as well as digitalis (10 trials; 1,401 patients), magnesium (14 trials; 1,853 patients), dexamethasone (1 trial; 216 patients), glucose-insulin-potassium (3 trials; 102 patients), insulin (1 trial; 501 patients), triiodothyronine (2 trials; 301 patients), and aniline (1 trial; 32 patients). A consistent finding in this review is that antiarrhythmic drugs with beta-adrenergic receptor-blocking effects (ie, class II beta-blockers, sotalol, and amiodarone) demonstrated successful prophylaxis. Furthermore, those therapies that did not inhibit beta-receptors generally failed to demonstrate a decreased incidence in postoperative AF. While sotalol and amiodarone have been shown in some studies to be effective, their safety and the incremental prophylactic advantage in comparison with beta-blockers has not been conclusively demonstrated. On the basis of evidence that has been reviewed and graded for quality, it is recommended that strong consideration should be given to the prophylactic administration of Vaughan-Williams class II beta-blocking drugs as a means of lowering the incidence of new-onset post-cardiac surgery AF.

Effects of the Postoperative Administration of Diltiazem on Renal Function After Coronary Artery Bypass Grafting

BACKGROUND

Radial artery grafts are used for coronary artery bypass grafting (CABG), and postoperative antispasm therapy with diltiazem is performed widely. Some investigators have warned that diltiazem administration after cardiac surgery is harmful to renal function. We designed a retrospective study to investigate the renal and hemodynamic effects of the postoperative administration of diltiazem in patients undergoing CABG.

METHODS

Subjects were 90 consecutive CABG patients. All were treated with diltiazem during surgery (a 0.1 mg/kg bolus injection followed by continuous infusion at 2 microg x kg(-1) x min(-1)). In the 50 patients (diltiazem group) with a radial artery graft, intravenous diltiazem administration was continued until the oral intake of diltiazem (90 mg/d) was begun to avoid graft spasms. In the remaining 40 patients without a radial artery graft, diltiazem was not continued postoperatively (control group). Postoperative renal function, assessed by serum creatinine level and creatinine clearance, and hemodynamic variables (heart rate, arterial pressure, pulmonary wedge pressure, cardiac index, left ventricular stroke work index) was compared between the two groups.

RESULTS

Renal function: Serum creatinine concentrations on postoperative days 1 through 7 were lower, and the endogenous creatinine clearance in the early postoperative period was higher in diltiazem group than in control group, although the differences were not significant. Hemodynamics: Heart rate was lower in diltiazem group than in the control group, but blood pressure, pulmonary wedge pressure, cardiac index, left ventricular stroke work index, and urinary output were similar between the groups.

CONCLUSIONS

Our results confirmed that intravenous diltiazem treatment in patients undergoing CABG is not harmful to renal function.

Pharmacologic Strategies for Prevention of Atrial Fibrillation After Open Heart Surgery

Postoperative atrial fibrillation is a common complication after open heart surgery; it increases morbidity, hospital stay, and costs. In an analysis of 8 large cardiac surgery trials totaling 20,193 patients, the incidence of postoperative atrial fibrillation was estimated to be 26% and ranged from 17% to 35%. We reviewed the results of 52 studies published between 1966 and 2003 that evaluated pharmacologic strategies to prevent postoperative atrial fibrillation in nearly 10,000 patients undergoing open heart operations. Supraventricular tachyarrhythmias, including atrial fibrillation, after open heart operations occurred in 29% of patients who did not receive prophylactic drugs, compared with 12% in patients who received intravenous followed by oral amiodarone, 15% in those given sotalol, 16% in those given oral amiodarone, and 19% in those given beta-blockers. Pharmacologic strategies and regimens aimed at preventing postoperative atrial fibrillation are necessary to optimize the postoperative care of patients undergoing open heart operations. Although no strategy has consistently been shown to be superior to another, the most effective approach to preventing postoperative atrial fibrillation likely involves multiple interventions. In the absence of contraindications, all patients should receive beta-blocker therapy before and after the operation. For patients with 1 or more risk factors for postoperative atrial fibrillation, regimens consisting of either sotalol (beta-blocker with class III antiarrhythmic properties) alone or beta-blockers in combination with amiodarone seem to be the safest, most effective pharmacologic strategies for preventing postoperative atrial fibrillation.

Strategies for perioperative arrhythmias

Rapid atrial arrhythmias affect close to one million elderly Americans who undergo cardiac or non-cardiac operations annually and have been associated with prolonged hospital stays. In contrast, bradyarrhythmias or ventricular arrhythmias severe enough to require treatment occur in less than 1% of patients who undergo all types of surgery, including cardiac. This article focuses on new issues leading to the improved understanding of the pathophysiology and mechanisms of post-operative atrial arrhythmias. New approaches directed at prophylaxis and acute therapy of atrial arrhythmias are discussed, as are recommendations to prevent thromboembolic events. Practice and research agenda are proposed.

A comparison between oral antiarrhythmic drugs in the prevention of atrial fibrillation after cardiac surgery: the pilot study of prevention of postoperative atrial fibrillation (SPPAF), a randomized, placebo-controlled trial

BACKGROUND

Atrial fibrillation (AF) frequently occurs after cardiac surgical procedures, and beta-blockers, sotalol, and amiodarone may reduce the frequency of AF after open heart surgery. This pilot trial was designed to test whether each of the active oral drug regimens is superior to placebo for prevention of postoperative AF and whether there are differences in favor of 1 of the preventive strategies.

METHODS AND RESULTS

We conducted a randomized, double-blinded, placebo-controlled trial in which patients undergoing cardiac surgery in the absence of heart failure and without significant left ventricular dysfunction (n = 253; average age, 65 +/- 11 years) received oral amiodarone plus metoprolol (n = 63), metoprolol alone (n = 62), sotalol (n = 63), or placebo (n = 65). Patients receiving combination therapy (amiodarone plus metoprolol) and those receiving sotalol had a significantly lower frequency of AF (30.2% and 31.7%; absolute difference, 23.6% and 22.1%; odds ratios [OR], 0.37 [95% CI, 0.18 to 0.77, P <.01 vs placebo] and 0.40 [0.19 to 0.82, P =.01 vs placebo]) compared with patients receiving placebo (53.8%). Treatment with metoprolol was associated with a 13.5% absolute reduction of AF (P =.16; OR, 0.58 [0.29 to 1.17]. Treatment effects did not differ significantly between active drug groups. Adverse events including cerebrovascular accident, postoperative ventricular tachycardia, nausea, and dyspepsia, in hospital death, postoperative infections, and hypotension, were similar among the groups. Bradycardia necessitating dose reduction or drug withdrawal occurred in 3.1% (placebo), 3.2% (combined amiodarone and metoprolol; P =.65 vs placebo), 12.7% (sotalol; P <.05 vs placebo), and 16.1% (metoprolol; P <.05 vs placebo). Patients in the placebo group had a nonsignificantly longer length of hospital stay as compared with the active treatment groups (13.1 +/- 8.9 days vs 11.3 +/- 7; P =.10), with no significant difference between the active treatment groups.

CONCLUSIONS

Oral active prophylaxis with either sotalol or amiodarone plus metoprolol may reduce the rate of AF after cardiac surgery in a population at high risk for postoperative AF. Treatment with metoprolol alone resulted in a trend to a lower risk for postoperative AF.

Off-pump coronary artery bypass surgery: physiology and anaesthetic management †

Increasing interest is being shown in beating heart (off-pump) coronary artery surgery (OPCAB) because, compared with operations performed with cardiopulmonary bypass, OPCAB surgery may be associated with decreased postoperative morbidity and reduced total costs. Its appears to produce better results than conventional surgery in high-risk patient populations, elderly patients, and those with compromised cardiac function or coagulation disorders. Recent improvements in the technique have resulted in the possibility of multiple-vessel grafting in all coronary territories, with a graft patency comparable with conventional surgery. During beating-heart surgery, anaesthetists face two problems: first, the maintenance of haemodynamic stability during heart enucleation necessary for accessing each coronary artery; and second, the management of intraoperative myocardial ischaemia when coronary flow must be interrupted during grafting. The anaesthetic technique is less important than adequate management of these two major constraints. However, experimental and recent clinical data suggest that volatile anaesthetics have a marked cardioprotective effect against ischaemia, and might be specifically indicated. OPCAB surgery requires team work between anaesthetists and surgeons, who must be aware of each other's constraints. Some surgical aspects of the operation are reviewed along with physiological and anaesthetic data.

Calcium antagonists reduce cardiovascular complications after cardiac surgery: a meta-analysis

OBJECTIVES

We sought to determine the efficacy of calcium antagonists (CAs) in reducing death, myocardial infarction (MI), ischemia, and supraventricular tachyarrhythmia (SVT) after cardiac surgery.

BACKGROUND

Calcium antagonists may reduce complications after cardiac surgery-namely, death, MI, and renal failure. However, they are underused, possibly due to the results from previous observational studies.

METHODS

Both MEDLINE (1966 to December 2001) and EMBASE (1980 to December 2001) were searched, with supplementation by reference list searches. No language restrictions were applied. Included studies were randomized, controlled trials (RCTs) evaluating preoperative, intraoperative, or postoperative (first 48 h) CA use (intravenous or oral) during aortocoronary bypass or valve surgery. Studies were excluded if they exclusively recruited transplant recipients, individuals <18 years old, or patients with pre-existing SVT. Two reviewers independently evaluated study quality by using the Jadad score; a minimal score of 1/5 was required. Forty-one studies, encompassing 3,327 patients, were included. No studies assessed treatment exclusively with short-acting oral nifedipine. Treatment effects were calculated using the random-effects model. Heterogeneity was assessed using the Q test.

RESULTS

Calcium antagonists significantly reduced MI (odds ratio [OR] 0.58, 95% confidence interval [CI] 0.37 to 0.91; p = 0.02) and ischemia (OR 0.53, 95% CI 0.39 to 0.72; p < 0.001). Non-dihydropyridines significantly reduced SVT (OR 0.62, 95% CI 0.41 to 0.93; p = 0.02). Calcium antagonists were associated with trends toward decreased mortality during aortocoronary bypass (OR 0.66, 95% CI 0.26 to 1.70, p = 0.4).

CONCLUSIONS

Use of CAs during cardiac surgery significantly reduced rates of MI, ischemia, and SVT. Further study using large RCTs is justified.

Pharmacotherapeutic considerations in anesthesia

This article focuses on new findings leading to improved understanding of the pathophysiology and mechanisms of potential drug interactions between anesthetic drugs or techniques and cardiovascular medications in patients scheduled for surgery. Only the most frequently used drugs are reviewed. Elective surgery provides the luxury to consider these risks and alter therapy accordingly. Under urgent circumstances, however, the increased risks associated with these agents should be anticipated with the goal to minimize adverse effects while maintaining optimal cardiovascular function in the perioperative period.

Diltiazem infusion for renal protection in cardiac surgical patients with preexisting renal dysfunction

OBJECTIVE

To evaluate if the calcium channel blocker diltiazem protects postoperatively renal function in cardiac surgical patients with preexisting mild-to-moderate renal dysfunction.

DESIGN

Prospective, randomized, placebo-controlled, double-blind, clinical study.

SETTING

Cardiothoracic anesthesia department at a university hospital.

PARTICIPANTS

Adult patients undergoing elective cardiac surgery using cardiopulmonary bypass, with a preoperatively elevated serum creatinine level (n = 24).

INTERVENTIONS

Randomized infusions of diltiazem (bolus 0.25 mg/kg followed by a continuous infusion of 1.7 microg/kg/min) (DTZ, n = 12) or placebo (C, n = 12) were started 30 minutes before induction of anesthesia and continued for 24 hours.

MEASUREMENTS AND MAIN RESULTS

Median plasma concentrations of diltiazem (DTZ group) were 79 microg/L before cardiopulmonary bypass, 67 microg/L at the end of cardiopulmonary bypass, and 164 microg/L at 24 hours postoperatively. Serum creatinine levels; on postoperative days 1, 3, and 5; and 3 weeks postoperatively were similar between groups. Iohexol clearance did not differ between the groups on day 5 but was higher in the DTZ group than in the placebo group 3 weeks after surgery (median, 51 v 40 mL/min/1.73 m(2); p < 0.05). Urinary N-acetyl-beta-glucosamidase concentrations were similar between the groups during the study but were increased from baseline on days 2 and 4 and 3 weeks postoperatively.

CONCLUSION

Diltiazem can be safely used in patients who have mild-to-moderate renal dysfunction and undergo cardiac surgery using cardiopulmonary bypass. Within the limits of this study, the data suggest that addition of prophylactic diltiazem may prevent further glomerular damage resulting from cardiopulmonary bypass and may improve glomerular function 3 weeks after cardiac surgery.

Postoperative atrial fibrillation

Postoperative atrial fibrillation is associated with significant morbidity, longer hospital stay, and higher related costs. Although the etiologic mechanism of postoperative atrial fibrillation and its optimum method of prophylaxis or management are not well defined, progress has been made during the past decade. This review focused on recent findings leading to a better understanding of the mechanisms and management of atrial fibrillation after surgery and current approaches directed at prevention of thromboembolic sequelae. Because postoperative atrial fibrillation is a frequent complication, preoperative risk assessment algorithms are being proposed to minimize the number of patients in whom an intervention to prevent atrial fibrillation is undertaken, and thus, reduce toxicity due to antiarrhythmic drug therapy. Finally, current data suggest that once atrial fibrillation has occurred, a rate-control strategy during the first 8 to 12 hours is reasonable because 50% of those episodes will resolve during this period. Beyond this period, a more aggressive approach using class IC or III antiarrhythmic drugs will hopefully reduce the number of patients requiring anticoagulation and prolonged drug therapy.

Atrial fibrillation after coronary surgery: comparison between different health care systems

AIMS

No studies have evaluated the influence of management strategies in different health insurance environments on atrial fibrillation (AF). This observational study compared the incidence of and treatment strategies for postoperative AF after primary coronary bypass surgery.

METHODS AND RESULTS

One insurance and one public funded location was compared: University of Michigan Health Center (USA, n=272) and Tampere University Hospital (Finland, n=314). USA patients had more co-morbidities and were treated more aggressively after acute myocardial infarction. More Finns were on beta-blockers both preoperatively (93 vs. 68%, P<0.001) and postoperatively (97 vs. 66%, P<0.001). However, AF was more frequent among Finns (38 vs. 29%, P=0.037) and present on 4.6% of cases when transferred postoperatively. No USA patients had AF at time of discharge. Mean length of stay was 8.6 days at USA, and not affected by AF. The incidence of in-hospital death, strokes and multiorgan failures was similar. Multivariable analysis, adjusted for site and selection biases (propensity analysis) revealed increasing age [OR=1.063 (1.042, 1.084), P<0.0001] and use of radial arteries [OR=2.175 (1.071, 4.417), P=0.032) to be independent predictors to the incidence of postoperative AF.

CONCLUSIONS

We found several major differences in patient selection and treatment strategies among primary coronary bypass patients managed in the two institutions. Despite the marked practice variation, the incidence of postoperative AF was rather similar. Despite routine use of beta-blockers, AF occurred in 29-38% of patients. However, the length of stay was not particularly affected by postoperative AF.

Diltiazem during reperfusion preserves high energy phosphates by protection of mitochondrial integrity

OBJECTIVE

This study evaluates the effects of diltiazem administered during reperfusion on hemodynamic, metabolic, and ultrastructural postischemic outcome.

METHODS

Hearts of 38 adult White New Zealand rabbits underwent 60 min of global cold ischemia followed by 40 min of reperfusion in an erythrocyte perfused isolated working heart model. Hearts were randomly assigned to four groups and received diltiazem (0.1, 0.25, and 0.5 micromol/l) during reperfusion only, or served as control.

RESULTS

The postischemic time courses of heart rate, aortic flow, and external stroke work clearly reflected the dose-dependent negative chronotropic and inotropic efficacy of diltiazem in the two higher concentrations. High energy phosphates (HEP) determined from myocardial biopsies taken after 40 min of reperfusion were significantly better preserved in all treatment groups compared to control hearts. Similarly ultrastructural grading of mitochondria and myofilaments revealed a significant reduction of reperfusion injury in hearts that received diltiazem compared to control.

CONCLUSIONS

Diltiazem protects mitochondrial integrity and function, thereby preserving myocardial HEP levels. Only low dose diltiazem (0.1 micromol/l) during reperfusion combines both, optimal mitochondrial preservation with minimal changes in hemodynamics.

Effects of preoperative treatment with diltiazem on diastolic ventricular function after coronary artery bypass graft surgery

OBJECTIVE

To examine whether preoperative treatment with diltiazem could ameliorate left ventricular (LV) diastolic dysfunction in patients after coronary artery bypass graft (CABG) surgery.

DESIGN

Prospective, nonrandomized clinical study.

SETTING

University hospital.

PARTICIPANTS

Thirty-four patients with preserved LV function undergoing elective CABG surgery.

INTERVENTIONS

According to medical history, patients were divided into 2 groups: patients not receiving diltiazem (n = 17) and patients treated with once-daily oral diltiazem for at least 2 weeks (n = 17). All patients received preoperative beta-blockers.

MEASUREMENTS AND MAIN RESULTS

After induction of anesthesia, after sternal closure, and 4 hours after cardiopulmonary bypass (CPB), mitral and pulmonary venous flow velocities were measured with pulsed Doppler. LV short-axis end-diastolic area by Doppler transesophageal echocardiography (TEE) and hemodynamic variables were obtained simultaneously at comparable pulmonary capillary wedge pressures. Postoperatively, increased peak E and A velocities were observed in patients with diltiazem and controls and returned to baseline 4 hours post-CPB in controls. Changes in these velocities did not result in a decreased E/A ratio. Peak A velocity, E/A ratio, and E wave deceleration time were significantly dependent on heart rate, not peak E velocity. End-diastolic area at comparable pulmonary capillary wedge pressure remained unchanged. In relation to diltiazem, only peak A velocity and time velocity integral of the A wave (TVI-A) at 4 hours post-CPB differed from controls.

CONCLUSION

Diastolic function is preserved after CABG surgery and is not altered by diltiazem in patients with preserved LV systolic function. The persistence of increased peak A velocity and TVI-A into the postoperative period suggests improved atrial systolic function with diltiazem.

Diltiazem Treatment Does Not Alter Renal Function After Thoracic Surgery

BACKGROUND

There are conflicting reports on the effects of diltiazem treatment on renal function in surgical patients. We sought to determine whether diltiazem treatment alters renal function in patients undergoing major thoracic surgery.

METHODS

In a prospective study, 330 patients scheduled for elective thoracic surgery received either IV diltiazem (n = 167) or placebo (n = 163) immediately after the operation and orally thereafter for 14 days in an effort to prevent postoperative atrial arrhythmias. Serum creatinine and BUN levels were compared before and during the first postoperative week.

RESULTS

Patients treated with diltiazem were similar to control subjects in terms of age (mean +/-SD, 66 +/- 10 years vs 67 +/- 10 years, respectively), baseline serum creatinine or BUN levels, prevalence of comorbid conditions, and surgical characteristics. During the first 5 postoperative days, the two groups did not differ in terms of serum creatinine or BUN levels. The incidence of renal failure was 0.6% in the diltiazem group and 1.2% in the placebo group (difference was not significant). There was no difference in the length of hospitalization or mortality rate.

CONCLUSIONS

In patients without renal disease who are undergoing elective thoracic surgery, prophylactic diltiazem treatment did not alter postoperative renal function.

Effects of diltiazem prophylaxis on the incidence and clinical outcome of atrial arrhythmias after thoracic surgery

OBJECTIVES

We sought to determine whether early prophylaxis with an L -type calcium channel blocker reduces the incidence and morbidity associated with atrial fibrillation/flutter and supraventricular tachyarrhythmia after major thoracic operations.

METHODS

In this randomized, double-blind, placebo-controlled study, 330 patients were given either intravenous diltiazem (n = 167) or placebo (n = 163) immediately after lobectomy (> or =60 years) or pneumonectomy (> or =18 years) and orally thereafter for 14 days. The primary end point with respect to efficacy was a sustained (> or =15 minutes) or clinically significant atrial arrhythmia during treatment.

RESULTS

Postoperative atrial arrhythmias (atrial fibrillation/flutter = 60; supraventricular tachyarrhythmias = 5) occurred in 25 (15%) of the 167 patients in the diltiazem group and 40 (25%) of the 163 patients in the placebo group (P = .03). When compared with placebo, diltiazem nearly halved the incidence of clinically significant arrhythmias (17/167 [10%] vs. 31/163 [19%], P = .02). The 2 groups did not differ in the incidence of other major postoperative complications or overall duration or costs of hospitalization. No serious adverse effects caused by diltiazem were seen.

CONCLUSIONS

After major thoracic operations, prophylactic diltiazem reduced the incidence of clinically significant atrial arrhythmias in patients considered at high risk for this complication.

Predictors of atrial fibrillation after conventional and beating heart coronary surgery: A prospective, randomized study

BACKGROUND

Atrial fibrillation (AF) increases the morbidity of CABG. The pathophysiology is uncertain, and its prevention remains suboptimal. This prospective, randomized study was designed to define the role of cardiopulmonary bypass (CPB) and cardioplegic arrest in the pathogenesis of this complication.

METHODS AND RESULTS

Two hundred patients were prospectively randomized to (1) on-pump conventional surgery [(100 patients, 79 men, mean age 63 (40 to 77) years)] with normothermic CPB and cardioplegic arrest of the heart or (2) off-pump surgery [(100 patients, 82 men, mean age 63 (38 to 86) years)] on the beating heart. Heart rate and rhythm were continuously monitored with an automated arrhythmia detector during the first 72 hours after surgery. Thereafter, routine clinical observation was performed and continuous monitoring restarted in the case of arrhythmia. The association of perioperative factors with AF was investigated by univariate analysis. Significant variables were then included into a stepwise logistic regression model to ascertain their independent influence on the occurrence of AF. There were no significant baseline differences between groups. Thirty-nine patients in the on-pump group and 8 patients in the off-pump group had postoperative sustained AF (P:=0.001). Univariate analysis showed that CPB inclusive of cardioplegic arrest, postoperative inotropic support, intubation time, chest infection, and hospital length of stay were predictors of AF (all P:<0.05). However, stepwise multivariate regression analysis identified CPB inclusive of cardioplegic arrest as the only independent predictor of postoperative AF (OR 7.4; CI 3.4 to 17.9).

CONCLUSIONS

CPB inclusive of cardioplegic arrest is the main independent predictor of postoperative AF in patients undergoing coronary revascularization.

Atrial fibrillation after cardiac operation: risks, mechanisms, and treatment

Atrial fibrillation (AF) is a common complication of cardiac operations that leads to increased risk for thromboembolism and excessive health care resource utilization. Advanced age, previous AF, and valvular heart operations are the most consistently identified risk factors for this arrhythmia. Dispersion of repolarization leading to reentry is believed to be the mechanism of postoperative AF, but many questions regarding the pathophysiology of AF remain unanswered. Treatment is aimed at controlling heart rate, preventing thromboembolic events, and conversion to sinus rhythm. Multiple investigations have examined methods of preventing postoperative AF, but the only firm conclusions that can be drawn is to avoid beta-blocker withdrawal after operation and to consider beta-blocker therapy for other patients who may tolerate these drugs. Preliminary investigations showing sotalol and amiodarone to be effective in preventing postoperative AF are encouraging, but early data have been limited to selective patient populations and have not adequately evaluated safety. Newer class III antiarrhythmic drugs under development may have a role in the treatment of postoperative AF, but the risk of drug-induced polymorphic ventricular tachycardia must be considered. Nonpharmacologic interventions under consideration for the treatment of AF in the nonsurgical setting, such as automatic atrial cardioversion devices and multisite atrial pacing, may eventually have a role for selected cardiac surgical patients.

Intravenous amiodarone for the prevention of atrial fibrillation after open heart surgery: the Amiodarone Reduction in Coronary Heart (ARCH) trial

OBJECTIVES

This study was designed to test whether intravenous (i.v.) amiodarone would prevent atrial fibrillation and decrease hospital stay after open heart surgery.

BACKGROUND

Atrial fibrillation commonly occurs after open heart procedures and is thought to be a significant determinant for prolongation of hospitalization. Oral amiodarone given preoperatively appears to reduce the incidence of atrial fibrillation. This study was designed to test whether the more rapid-acting i.v. formulation of amiodarone given postoperatively would reduce the incidence of atrial fibrillation.

METHODS

Three hundred patients undergoing standard open heart surgery were randomized in a double-blind fashion to i.v. amiodarone (1 g/day for 2 days) versus placebo immediately after open heart surgery. The primary end points of the trial were incidence of atrial fibrillation and length of hospital stay. Baseline clinical variables and mortality and morbidity data were collected.

RESULTS

Atrial fibrillation occurred in 67/142 (47%) patients on placebo versus 56/158 (35%) on amiodarone (p = 0.01). Length of hospital stay for the placebo group was 8.2 +/- 6.2 days, and 7.6 +/- 5.9 days for the amiodarone group (p = 0.34). No differences were noted in baseline variables, morbidity or mortality.

CONCLUSIONS

Low-dose i.v. amiodarone was safe and effective in reducing the incidence of atrial fibrillation after heart surgery, but did not significantly alter length of hospital stay.

Preoperative cardiac preparation

Preoperative preparation of the cardiac patient is based on matching the cardiac reserve to the blood flow demands imposed by surgical stress and the underlying disease state. Evaluation must include functional assessment of any coronary artery disease or other organic cardiac disease that may place myocardial tissue at risk of ischemia as demand for cardiac output increases. Monitoring should be individualized based on anticipated problems and the risk assessment of the patient. Preoperative therapy should include maneuvers that reduce congestive heart failure, optimize volume status, and provide adequate cardiac output to deliver oxygen sufficient to meet or exceed demand. Underlying electrical and metabolic abnormalities should be corrected and controlled in the perioperative period. Long-term therapy should be evaluated and modified in the context of the anesthetic and surgical plan. Preventive interventions such as fluid loading and low-dose dopamine should be considered prior to surgery.

Beating versus arrested heart revascularization: evaluation of myocardial function in a prospective randomized study

OBJECTIVE

Conventional coronary artery bypass grafting (CABG) is both safe and effective. Nevertheless, the use of cardiopulmonary bypass (CPB) and cardioplegic arrest are associated with several adverse effects. Over the last 2 years there has been a revival of interest in performing CABG on the beating heart. In this prospective randomized study we evaluated the efficacy and safety of on and off pump coronary revascularization on myocardial function.

METHODS

Eighty patients (65 males, mean age 61+/-9.7 years) undergoing first time CABG were prospectively randomized to: (i) conventional revascularization with CPB at normothermia and cardioplegic arrest with intermittent warm blood cardioplegia (on pump) or (ii) beating heart revascularization (off pump). Troponin I (Tn I) release was serially measured as a specific marker of myocardial damage. Haemodynamic measurements as well as inotropic requirement, incidence of arrhythmia and postoperative myocardial infarction were also recorded.

RESULTS

There were no significant differences between the two groups in terms of age, sex, extent of disease, left ventricular function and number of grafts. There were no deaths or intraoperative myocardial infarctions in either group. Tn I release was constantly lower in the off pump group and this was significant at 1, 4, 12 and 24 h postoperatively. Furthermore, in this group there was a significantly reduced incidence of arrhythmias. Inotropic requirements were less in the off pump group but this did not reach statistical significance.

CONCLUSION

These results suggest that off pump coronary revascularization is a safe and effective strategy for myocardial revascularization. Myocardial injury as assessed by Tn I release is also reduced when compared with conventional coronary revascularization with CPB and cardioplegic arrest.

Intravenous diltiazem and acute renal failure after cardiac operations

BACKGROUND

Perioperative administration of intravenous diltiazem to patients undergoing cardiac procedures has been shown to decrease the incidence of ischemia and arrhythmias. However, after adopting this practice in our cardiac surgery program, we perceived an increased incidence of postoperative renal dysfunction.

METHODS

A directed record review of postoperative renal function was conducted for consecutive patients undergoing cardiac operation for the time periods before and after adoption of prophylactic intravenous diltiazem (0.1 mg.kg-1.h-1 for 24 hours). The two groups were compared using chi 2 and two-sample t tests. The risk of development of postoperative renal failure was modeled with logistic regression.

RESULTS

Diltiazem-treated patients (n = 271) were similar to the control patients (n = 143) in terms of age (64 versus 61 years; p = 0.14), ejection fraction (0.46 versus 0.47; p = 0.61), baseline serum creatinine level (1.2 versus 1.1 mg/dL; p = 0.27), prevalence of comorbid conditions, and surgical characteristics. The prevalence of left main coronary artery disease was lower in the diltiazem group than the control group (39% versus 52%; p = 0.01). During the 7-day postoperative period, the average peak serum creatinine level was higher in the diltiazem group (1.7 +/- 0.9 mg/dL; mean +/- 1 standard deviation) than the control group (1.5 +/- 0.5 mg/dL; p = 0.003). The incidence of acute renal failure requiring dialysis was 4.4% in the diltiazem group versus 0.7% in the control group (p = 0.04). There was no difference in length of hospitalization or mortality. The risk of acute renal failure was strongly associated with intravenous diltiazem (adjusted odds ratio [AOR] 6.3; p = 0.08), age (AOR 2.5 per 10 years; p = 0.07), baseline serum creatinine (AOR 4.8 per 1 mg/dL; p = 0.02), the presence of left main coronary disease (AOR 5.3; p = 0.02), and the presence of cerebrovascular disease (AOR 4.5; p = 0.05).

CONCLUSIONS

Our retrospective analysis suggests that prophylactic use of intravenous diltiazem in patients undergoing cardiac operations was associated with increased renal dysfunction. Further studies of the risk and benefits of intravenous diltiazem in this setting should be undertaken.

Postoperative Cardiac Arrhythmias: Prevention and Management

Supraventricular arrhythmias or supraventricular tachy cardias (SVT) frequently occur after thoracic surgery and have been associated with prolonged hospital stays. The reported incidence of supraventricular ar rhythmias in this patient population ranges from 9% to 40%, with factors such as extent of surgery markedly influencing the incidence. SVT has been reported to be 12% to 16% after lobectomy, 20% to 30% after pneumo nectomy, and as much as 40% after extrapleural pneu monectomy for malignant pleural mesothelioma. Pa tients who develop SVT have a higher rate of intensive care unit admission and higher 30-day mortality. SVT occurrence appears to be an important marker of poor cardiopulmonary reserve in patients who developed significant morbidity after thoracic surgery. It is pos sible that the rate of SVT occurrence increases propor tionally with extent of neural trauma to cardiac plexus structures in older patients. The timing of SVT onset is likely related to the high adrenergic activity of the postsurgery state and the resolution of a graded inflam matory process corresponding to the amount of blunt or sharp surgical trauma to sympathovagal nerve fibers innervating the sinus node. This article will focus on new issues leading to improved understanding of the pathophysiology and mechanisms of SVT after surgery. New approaches directed at prophylaxis and acute therapy of SVT are also discussed.

An electrocardiographic lead system for coronary artery bypass surgery

STUDY OBJECTIVES

To identify the optimal subset of two electrocardiographic (ECG) leads for monitoring of ischemic ST depression and elevation during coronary artery bypass grafting (CABG) surgery.

DESIGN

Prospective observational clinical study.

SETTING

University hospital cardiac surgery operating room.

PATIENTS

120 patients undergoing primary surgery or reoperation for CABG.

INTERVENTIONS

All six ECG limb leads and a precordial matrix of four leads were recorded intraoperatively approximately every 3 minutes. The limb leads were placed on the torso in modified Mason-Likar positions. The precordial leads were placed at V4, V5, and one interspace below them.

MEASUREMENTS AND MAIN RESULTS

New ischemic 1 mm ST depression and elevation episodes were determined. New ST deviation episodes attributed to nonischemic causes such as cooling at the onset of cardiopulmonary bypass (CPB), defibrillation at the end of CPB, new cardiac conduction changes after CPB, and postoperative pericarditis were excluded. Fixed ST deviation that did not change by 1 mm in the perioperative period was also excluded. Leads V5 and III constituted the best two-lead set. These leads recorded 15 of the 16 ischemic ST elevation episodes and all 8 ischemic ST depression episodes. One ST elevation episode was not recorded intraoperatively but was recorded in lead V1 in the immediate postoperative ECG. Leads V5 and II recorded 13 of the 16 ischemic ST elevation episodes and all 8 ischemic ST depression episodes. Lead V5 alone missed 8 episodes of ischemic ST elevation and one episode of ischemic ST depression.

CONCLUSIONS

For monitoring of ischemia during CABG, leads V5 and III are preferable to other two-lead sets, including the commonly used V5 and II. No single lead is adequate. Lead V5 alone missed approximately one half the episodes of ST elevation that were recorded by lead III or another inferior lead.

Comparison of perioperative myocardial protection with nifedipine versus nifedipine and metoprolol in patients undergoing elective coronary artery bypass grafting

A randomized study was performed on 70 patients undergoing elective coronary bypass grafting to examine whether the combined infusion of the calcium channel blocker nifedipine (10 micrograms/kg per hour) and the beta 1-blocker metopropol (12 micrograms/kg per hour, n = 34) reduces the prevalence of perioperative myocardial ischemia and arrhythmias. The control group received nifedipine alone (n = 36). In both groups the infusion was started from the onset of extracorporal circulation and maintained over a period of 24 hours. Repeated 12-lead electrocardiographic and 3-channel Holter monitor recordings for 48 hours were used to define perioperative myocardial ischemia (transient ischemic event, myocardial infarction) and arrhythmias (sinus tachycardia, supraventricular tachycardia, atrial flutter/fibrillation, ventricular tachycardia). Hemodynamic parameters were repeatedly assessed for 24 hours and serum enzyme levels (creatine kinase, MB isoenzyme of creatine kinase) for up to 36 hours after the operation. The two groups did not differ significantly with respect to preoperative anamnestic and surgical data. No signs of perioperative myocardial infarction were detected in either group. However, a significantly lower incidence of transient ischemic episodes was observed in the nifedipine-metoprolol group than in the nifedipine group (3% vs 11%; p < 0.05). In addition, there was a tendency toward lower creatine kinase MB levels and peak values of creatine kinase and creatine kinase MB in the nifedipine-metoprolol group. With regard to perioperative arrhythmias, there was a significantly lower incidence of sinus tachycardia and atrial flutter/fibrillation in the nifedipine-metoprolol group (9% and 6%) than in the nifedipine group (33% and 27%, p < 0.05). In addition, postoperative heart rate was lower in the nifedipine-metoprolol group starting from the sixth hour after release of the aortic crossclamp (p < 0.05 and p < 0.01, respectively). No other hemodynamic parameters showed significant differences between the two groups and all returned to preoperative levels within 24 hours. In conclusion, perioperative application of nifedipine and metoprolol in patients undergoing elective coronary bypass grafting reduces the prevalence of perioperative myocardial ischemia and arrhythmias without significant negative inotropic effects. The combined infusion of the two drugs appears superior to nifedipine alone in preventing perioperative myocardial ischemia and reducing reperfusion-induced arrhythmias.

Myocardial injury during reoperation for coronary artery bypass surgery

OBJECTIVES

To determine the incidence, triggers, and timing of myocardial injury during reoperation for coronary artery bypass surgery.

DESIGN

Prospective observational.

SETTING

One tertiary care university hospital.

PARTICIPANTS

15 patients undergoing reoperation.

INTERVENTIONS

Multilead electrocardiographic monitoring approximately every 3 minutes during surgery.

MEASUREMENTS AND MAIN RESULTS

The occurrence of a new ischemic ST elevation or depression on the electrocardiogram (ECG) was determined. A major deterioration in ventricular function after cardiopulmonary bypass (CPB) also was determined. Peak creatine kinase myocardial band (CK-MB) > or = 25 IU/L was considered to be the marker of myocardial injury. Seven patients demonstrated myocardial injury, all intraoperatively. Five of these patients had new ST elevation episodes before CPB. Three of the episodes were temporally associated with an abrupt increase in the heart rate. The other two episodes were temporally associated with surgical manipulation of the heart and the old grafts. The sixth patient had a significant deterioration of ventricular function during CPB. One of the patients who had ST elevation before CPB and the seventh patient developed ST elevation towards the end of protamine administration.

CONCLUSIONS

In patients undergoing reoperation, the intraoperative incidence of myocardial injury, especially before CPB, was found to be substantially higher than that previously reported.

Myocardial ischemia after cardiopulmonary bypass

Intraoperatively, myocardial ischemia is more common after cardiopulmonary bypass (CPB) than before CPB. Ischemia associated with coronary vasospasm and thrombosis may be much more common toward the end of surgery and early in the postoperative period than previously appreciated. This may be because the coagulation system is altered during CPB, and the coronary endothelium is damaged significantly as a result of cardioplegic arrest followed by reperfusion. In this milieu, vasospasm and thrombosis may be caused by the administration of protamine. Some of the ischemia observed in this period actually is not reversible and is associated with myocardial injury and infarction. It may be ameliorated by the administration of calcium channel blockers, aspirin, and anticoagulants. Electrocardiography may be the most suitable modality for the detection of ischemia after CPB and postoperatively. During this period, many episodes of ST deviation are of a nonischemic etiology, and the ECG needs careful interpretation. Transesophageal echocardiography is suitable for use intraoperatively and early on in the intensive care unit.

Effects of magnesium on myocardial function after coronary artery bypass grafting

The effects of perioperative administration of magnesium sulfate on myocardial function was studied in patients with unstable angina (grade IV) undergoing coronary artery bypass grafting. Myocardial protection consisted of antegrade and retrograde continuous warm blood cardioplegia. Patients were randomly divided into two groups. Group A (50 patients) received intravenous magnesium sulfate (16 mmol) continuously from the time of anesthetic induction to aortic cross-clamping and a second dose (32 mmol) starting after the release of aortic cross-clamp until 24 hours later. Group B (48 patients) did not receive magnesium sulfate and served as control. Left ventricular stroke work index increased in group A from 34 +/- 3 g.m/m2 before operation to 42 +/- 3 g.m/m2, 45 +/- 2 g.m/m2, and 47 +/- 2 g.m/m2, 1, 6, and 12 hours after operation, respectively (p < 0.05 versus preoperative), and in group B from 33 +/- 3 g.m/m2 before operation to 38 +/- 3 g.m/m2, 40 +/- 2 g.m/m2, and 41 +/- 2 g.m/m2, 1, 6, and 12 hours after operation, respectively (p < 0.05). Left ventricular stroke work index was higher in group A 6 (p = 0.06), 12, and 24 hours (p < 0.05) after operation compared with group B. The incidence of ventricular arrhythmias requiring treatment was significantly higher (p < 0.05) in group B: 14 patients versus 1 patient in group A. Postoperative hypertension was more frequent in group B: 16 patients versus 2 patients in group A (p < 0.05). These results indicate that perioperative administration of magnesium sulfate may contribute to better myocardial recovery and fewer ventricular tachyarrhythmias after operation.