Preoperative heart rate and myocardial injury after non-cardiac surgery: results of a predefined secondary analysis of the VISION study

Background

Increased baseline heart rate is associated with cardiovascular risk and all-cause mortality in the general population. We hypothesized that elevated preoperative heart rate increases the risk of myocardial injury after non-cardiac surgery (MINS).

Methods

We performed a secondary analysis of a prospective international cohort study of patients aged ≥45 yr undergoing non-cardiac surgery. Preoperative heart rate was defined as the last measurement before induction of anaesthesia. The sample was divided into deciles by heart rate. Multivariable logistic regression models were used to determine relationships between preoperative heart rate and MINS (determined by serum troponin concentration), myocardial infarction (MI), and death within 30 days of surgery. Separate models were used to test the relationship between these outcomes and predefined binary heart rate thresholds.

Results

Patients with missing outcomes or heart rate data were excluded from respective analyses. Of 15 087 patients, 1197 (7.9%) sustained MINS, 454 of 16 007 patients (2.8%) sustained MI, and 315 of 16 037 patients (2.0%) died. The highest heart rate decile (>96 beats min⁻¹) was independently associated with MINS {odds ratio (OR) 1.48 [1.23–1.77]; P<0.01}, MI (OR 1.71 [1.34–2.18]; P<0.01), and mortality (OR 3.16 [2.45–4.07]; P<0.01). The lowest decile (<60 beats min⁻¹) was independently associated with reduced mortality (OR 0.50 [0.29–0.88]; P=0.02), but not MINS or MI. The predefined binary thresholds were also associated with MINS, but more weakly than the highest heart rate decile.

Conclusions

Preoperative heart rate >96 beats min⁻¹ is associated with MINS, MI, and mortality after non-cardiac surgery. This association persists after accounting for potential confounding factors.

Clinical trial registration

NCT00512109.

Does a 'direct' transfer protocol reduce time to coronary angiography for patients with non-ST-elevation acute coronary syndromes? A prospective observational study

OBJECTIVE

National guidelines recommend 'early' coronary angiography within 96 h of presentation for patients with non-ST elevation acute coronary syndromes (NSTE-ACS). Most patients with NSTE-ACS present to their district general hospital (DGH), and await transfer to the regional cardiac centre for angiography. This care model has inherent time delays, and delivery of timely angiography is problematic. The objective of this study was to assess a novel clinical care pathway for the management of NSTE-ACS, known locally as the Heart Attack Centre-Extension or HAC-X, designed to rapidly identify patients with NSTE-ACS while in DGH emergency departments (ED) and facilitate transfer to the regional interventional centre for 'early' coronary angiography.

METHODS

This was an observational study of 702 patients divided into two groups; 391 patients treated before the instigation of the HAC-X pathway (Pre-HAC-X), and 311 patients treated via the novel pathway (Post-HAC-X). Our primary study end point was time from ED admission to coronary angiography. We also assessed the length of hospital stay.

RESULTS

Median time from ED admission to coronary angiography was 7.2 (IQR 5.1-10.2) days pre-HAC-X compared to 1.0 (IQR 0.7-2.0) day post-HAC-X (p<0.001). Median length of hospital stay was 3.0 (IQR 2.0-6.0) days post-HAC-X v 9.0 (IQR 6.0-14.0) days pre-HAC-X (p<0.0005). This equates to a reduction of six hospital bed days per NSTE-ACS admission.

CONCLUSIONS

The introduction of this novel care pathway was associated with significant reductions in time to angiography and in total hospital bed occupancy for patients with NSTE-ACS.

Screening for carotid artery disease before cardiac surgery: is current clinical practice evidence based?

BACKGROUND

There is no clear consensus as to the correct screening procedure to identify patients undergoing cardiac surgery and who are at greatest risk of stroke because of the presence of significant carotid artery stenosis. Such screening is important because some patients benefit from combined carotid and cardiac surgery and, regardless of this, the information gained puts the cardiac surgeon in a position to provide an accurate assessment of surgical risk. Our objective was to examine current clinical practice of carotid artery investigation prior to urgent cardiac surgery and to review this illustrative practice in the context of the world literature.

HYPOTHESIS

The study aimed to establish that current typical practice for screening cardiac surgical patients for carotid artery disease is illogical according to the evidence in the world literature.

METHODS

The study consisted of a retrospective assessment of all patients undergoing urgent cardiac surgery and a Medline-derived literature review, and included all patients undergoing urgent cardiac surgery at a tertiary cardiothoracic center between January 1 and December 31, 1997.

RESULTS

Of 529 patients undergoing urgent cardiac surgery, 44 (8%) were screened preoperatively by duplex Doppler ultrasonography for carotid disease. The indications for screening were asymptomatic carotid bruit in 24 patients, history of stroke or transient ischemic attack (TIA) in 12 patients, and neither stroke, TIA, or bruit in 7 patients. The tests were requested either by the attending cardiologists or by the cardiac surgeon to whom they were referred. One patient had already been diagnosed as having carotid artery disease in the past. Thirteen patients underwent additional carotid investigations. Eleven patients were demonstrated to have internal carotid artery stenosis > or = 60% and 3 patients underwent combined cardiac and carotid surgery. Review of the literature revealed the following groups to be at increased risk of future stroke unrelated to surgery, and of postoperative stroke: those with a history of stroke or TIA, those with carotid bruits, and, of importance, all patients with significant carotid stenosis. Recent data suggest that symptomatic patients and the elderly are at greatest risk.

CONCLUSIONS

Only 8% of patients undergoing urgent cardiac surgery in a 1-year period were screened for carotid artery disease. We suggest that screening should definitely be performed in all patients with a history of stroke or TIA, all patients with a bruit, and all patients aged > 65 years. The literature suggests, however, that significant reductions in stroke rate could be achieved by screening the whole cardiac surgical population, although there is a paucity of data that are specifically pertinent to this patient subgroup. Further data are therefore required for the construction of a scientifically valid and medicolegally sound policy.

Paraprosthetic leak unmasked by thrombolysis for thrombosed mitral valve

Prosthetic valve thrombosis (PVT) is classically a cardiothoracic surgical emergency. Case series, however, report thrombolysis as first line management for PVT. A case of mitral PVT treated successfully with thrombolysis is described. Immediately after thrombolysis a trivial paraprosthetic leak noted on pretreatment transoesophageal echocardiography had increased significantly in severity. The paraprosthetic leak subsequently required repeat mitral valve replacement. It is speculated that the thrombolytic treatment interfered with the usual healing process by disrupting the fibrin deposited at the valve ring margin. This suggests that fibrin is important in the formation of the annular seal of the prosthetic valve and that patients receiving thrombolysis should be monitored for this complication.

Atrial pacing for the prevention of atrial fibrillation after coronary artery bypass graft surgery: a review of the literature

Atrial fibrillation (AF) occurs in 20-40% of patients after coronary artery bypass graft surgery (CABG) and contributes to increased morbidity and expenditure after CABG. The limited efficacy of pharmacological treatment to prevent post-CABG AF has stimulated research into alternative prophylactic strategies for the arrhythmia. This article critically reviews the trial evidence in the literature regarding the efficacy of epicardial atrial pacing to prevent post-CABG AF. Thirteen randomised controlled trials of either right, left, or biatrial pacing to prevent post-CABG AF were identified. Overall, prophylactic biatrial epicardial pacing appears to be effective prophylaxis against post-CABG AF and to reduce postoperative hospital stay. The efficacy of single site right or left atrial pacing is less clear. Further data are required to determine both the efficacy of single site atrial pacing and the cost effectiveness of pacing strategies to prevent AF after CABG.

Off-pump coronary artery bypass graft surgery: the incidence of postoperative atrial fibrillation

Atrial fibrillation (AF) occurs in one quarter to one third of patients after coronary artery bypass graft surgery (CABG). Conventional CABG uses cardiopulmonary bypass, a process that is itself associated with a systemic vascular inflammatory response that contributes to postoperative morbidity. The avoidance of cardiopulmonary bypass is associated with a significant reduction in the inflammatory response and in the release of markers of myocardial necrosis when compared with conventional CABG. There is speculation that off-pump CABG may reduce the incidence of postoperative AF through reduced trauma, ischaemia, and inflammation. Current data, however, do not emphatically answer the question of whether the incidence of post-CABG AF is reduced by off-pump surgery. The evidence from both observational and randomised studies is conflicting and many studies have weaknesses in design, conduct, or interpretation. It remains an attractive hypothesis that postoperative AF is reduced by off-pump CABG but more robust data are required.

Magnesium for atrial fibrillation after coronary artery bypass graft surgery: its role in aetiology and prevention

OBJECTIVE

To summarise the potential consequences of atrial fibrillation (AF) after coronary artery bypass graft surgery (CABG) and the relationship of the arrhythmia with serum magnesium concentration ([Mg]) and to review the trials of magnesium supplementation as prophylaxis against post-CABG AF.

DATA SOURCES

Abstracts, articles and published reviews on AF after CABG and magnesium prophylaxis.

SUMMARY OF REVIEW

AF after CABG occurs in 20-40% of patients. It may cause haemodynamic compromise, stroke, prolongation of hospital stay and an increased use of resources. Effective prophylaxis offers the enticing prospect of reductions in morbidity, hospital stay and resource utilisation. There is circumstantial evidence suggesting that hypomagnesaemia may predispose to cardiac arrhythmias. Serum [Mg] falls after CABG due to haemodilution and beta-adrenergic mediated mechanisms. Several studies have reported an association between hypomagnesaemia and post-CABG AF, but a causal relationship has not been established. Trials have demonstrated that magnesium (Mg) replacement can attenuate the perioperative fall in serum [Mg], but have failed to show efficacy of Mg therapy in AF prevention after CABG. The perioperative changes in serum [Mg] do not seem to reflect changes in intracellular magnesium, including within the atria.

CONCLUSIONS

AF after CABG is common and a drain on resources through its association with increased morbidity and hospital stay. Previous studies investigating the relationship between serum [Mg] and AF after CABG have produced inconsistent results. The current evidence from randomised, placebo-controlled trials does not support the use of Mg therapy to prevent AF after CABG and strengthens the likelihood of any association between post-CABG AF and hypomagnesaemia being a passive one. That Mg appears ineffective as prophylaxis for postoperative AF may partly be due to limitations in trial methodology, but most probably reflects the poor correlation between serum total [Mg] and intracellular magnesium, specifically the intra-atrial magnesium content.

Prognostic implications of ventricular fibrillation in acute myocardial infarction: new strategies required for further mortality reduction

OBJECTIVE

To determine the changing risk of ventricular fibrillation, the prognostic implications, and the potential long term prognostic benefit of earlier hospital admission, after acute myocardial infarction.

DESIGN

Prospective observational study.

SETTING

A district general hospital in east London.

PATIENTS

1225 consecutive patients admitted to a coronary care unit with acute myocardial infarction.

MAIN OUTCOME MEASURES

Time of onset of pain and ventricular fibrillation, and long term survival of patients admitted with acute myocardial infarction.

RESULTS

The rate of ventricular fibrillation in these hospital inpatients was high in the first hour from onset of pain (118 events/1000 persons/h; 95% confidence interval (CI) 50.7 to 231) and fell rapidly to an almost constant low level by six hours; 27.4% of patients with early ventricular fibrillation died in hospital, compared with 11.6% of those without (p < 0.0001), but mortality in patients who survived to hospital discharge was not altered by early ventricular fibrillation (five year survival: 75.0% (95% CI 60.0% to 84.8%) with ventricular fibrillation v 73.3% (95% CI 69.6% to 76.6%) without ventricular fibrillation).

CONCLUSIONS

Patients successfully resuscitated from early ventricular fibrillation have the same prognosis as those without ventricular fibrillation after acute myocardial infarction. Faster access to facilities for resuscitation must be achieved if major improvements in the persistently high case fatality of patients after acute myocardial infarction are to be made.

Atrial fibrillation after coronary artery bypass surgery: a model for preoperative risk stratification

BACKGROUND

Atrial fibrillation (AF) occurs in 20% to 40% of patients after CABG. Identification of patients vulnerable for arrhythmia will allow targeting of those most likely to benefit from prophylactic therapy. The aim of the present study was to evaluate accuracy of a prospectively defined signal-averaged P-wave duration (SAPD) cutoff and additional preoperative characteristics for the prediction of AF after CABG.

METHODS AND RESULTS

Patients undergoing elective isolated CABG were recruited to the present prospective study. SAPD was recorded in all patients. Filtered signals from 3 orthogonal leads were combined in a vector analysis, and total SAPD was measured preoperatively. Postoperative in-hospital AF occurred in 92 (28.2%) of 326 patients. Patients who developed AF were older (65.9 versus 61.7 years of age; P<0.0005) and had longer SAPD (158 versus 145 ms; P<0.0005) than non-AF patients. Incidence of AF increased in patients > or =75 years of age and increased progressively throughout the range of SAPD. Stepwise logistic regression analysis of preoperative variables identified that SAPD >155 ms (odds ratio, 5.37; 95% CI, 3.10 to 9.30; P<0.0005), advanced age (odds ratio, 1. 53; 95% CI, 1.26 to 1.86 per 5-year increase in age; P<0.0005), and male sex (odds ratio, 2.88; 95% CI, 1.30 to 6.40; P<0.01) independently predicted AF. Prospectively defined SAPD >155 ms predicted AF with positive and negative predictive accuracy of 49% and 84%, respectively.

CONCLUSIONS

A combination of prolonged SAPD, advanced age, and male sex identifies patients at high risk for development of AF after CABG.

Modification of coronary artery disease progression by cholesterol-lowering therapy: the angiographic studies

Large randomized placebo-controlled trials have demonstrated that cholesterol lowering with statin therapy reduces the incidence of adverse cardiac events. Smaller angiographic studies have shown that coronary artery disease progression can be slowed and, in some cases, reversed by cholesterol-lowering interventions. These anatomical changes, however, are small and occur too slowly to account for the early clinical benefit. Current evidence suggests that plaque stabilization is the most important mechanism, by which cholesterol-lowering therapy reduces both the incidence of adverse cardiac events and coronary artery disease progression.

Long-term follow-up of a true contractile left ventricular diverticulum

The natural history of contractile left ventricular diverticulum in the adult is not known. Serial left ventricular angiography in an adult revealed that a left ventricular diverticulum did not increase in size over a 13-year period, suggesting that the clinical course may be benign.

Computer-generated correspondence for patients attending an open-access chest pain clinic

AIM

To determine whether general practitioners (GPs) prefer structured computer-generated or standard dictated outpatient clinic letters.

DESIGN

Questionnaire survey of all GPs referring patients to an open-access chest pain clinic at a district general hospital in London. The GPs were asked to compare three twinned examples of structured computer-generated and unstructured dictated letters.

RESULTS

Of 93 respondents (response rate 77.5%), 75 (80.6%) preferred the computer-generated letter and 16 (17.2%) preferred the dictated letter (p < 0.0005). The preferred features of the computer-generated letter were its clear presentation, subheadings, and concise information. The computer-generated letter scored significantly higher than the dictated letter: for clarity, mean 8.2 vs 6.5 (p < 0.0005); content, mean 8.5 vs 6.9 (p < 0.0005); and readability, mean 8.2 vs 6.8 (p < 0.0005). The GPs in the survey considered a mean delay of 3.4 days to be acceptable for receiving the letter from the chest pain clinic.

CONCLUSION

GPs prefer structured computer-generated letters to unstructured dictated letters for patients referred to an open-access chest pain clinic. Computer-generated correspondence allows rapid feedback of information to the referring GP, one of the key requirements of open-access clinics.

Frequency and prognostic implications of conduction defects in acute myocardial infarction since the introduction of thrombolytic therapy

OBJECTIVE

To document the frequency of conduction defects and their influence on prognosis in a large series of patients with acute myocardial infarction who underwent coronary care during a period when thrombolytic therapy was in common usage.

BACKGROUND

Conduction defects have been associated with an adverse prognosis following acute myocardial infarction, but there are few data on the incidence and outcome of conduction defects since the introduction of thrombolytic therapy.

PATIENTS AND METHODS

The study group comprised 1225 consecutive patients with acute myocardial infarction treated in the coronary care unit from 1 January 1988 to 31 December 1994. Conduction defects were recorded prospectively and were classified as follows: complete atrioventricular node block associated with narrow complex escape rhythms; left or right bundle branch block; bifascicular block; complete heart block involving both bundle branches.

RESULTS

Electrocardiographic data were available in 1220 patients. Complete atrioventricular node block occurred in 65 (5.3%), left and right bundle branch block in 29 (2.4%) and 44 (3.6%) bifascicular block in 36 (2.9%) and complete heart block involving both bundle branches in 20 (1.6%). The more advanced degrees of block in the bundle branches occurred more commonly in patients with diabetes, previous infarction. Q-wave infarction, anterior infarction and left ventricular failure. Survival analysis showed an increased short- and long-term cardiac mortality in patients with conduction defects, prognosis worsening as the severity of the conduction defect increased.

CONCLUSION

Conduction defects complicated acute myocardial infarction in 16% of cases and had a graded impact on the short- and long-term prognosis, patients with advanced bundle branch involvement faring worst. The data showed a small decline in the rate of severe conduction defects compared with previous studies, possibly reflecting the beneficial effects of thrombolytic therapy on infarct size.

Evaluation of a computer-generated discharge summary for patients with acute coronary syndromes

The discharge summary from hospital to community physician contributes importantly to patient management, but deficiencies in its preparation are well documented. We sought to determine the preferences of general practitioners for standard dictated or computer-generated discharge summaries for patients with acute coronary syndromes. The majority (68.5%) of GPs preferred the computerized summary and particularly liked its comprehensive content, concise style, ease of access to relevant information, clarity and ease of reading. Most (66.9%) thought the computer-generated summary provided the clearer management plan and 70.8% recommended its use for other specialities. In addition, its speed of generation enables GPs to receive a summary within seven days of patient discharge.