Abnormal electrocardiograms and cardiovascular risk: role of silent myocardial ischemia. Evidence from MRFIT

The potential yield of ECG screening of hypertensive patients: the Utrecht Health Project

OBJECTIVE

Several guidelines for hypertension and cardiovascular risk management recommend an ECG in hypertensive patients to improve risk prediction. We estimated the prevalence of clinically relevant ECG abnormalities and the number needed to screen (NNS) with a routine ECG to prevent the occurrence of one death in the next 10 years conditional on adequate treatment and follow-up.

METHODS

The study population consisted of 866 hypertensive participants recruited from the Utrecht Health Project (UHP), a dynamic population study in Utrecht. Baseline measurements included an ECG and the risk factors that enable a Systematic COronary Risk Evaluation (SCORE) risk estimation for each participant. ECGs were interpreted using Modular ECG Analysis System for computerized recognition of ECG abnormalities. NNS to prevent one death was computed by the reciprocal of the prevalence of the ECG abnormalities multiplied by number needed to treat to prevent one death when the ECG abnormality is managed according to the prevailing clinical guidelines.

RESULTS

The population consisted of 54.2% men with a mean age of 53.2 years (SD 11.5). The prevalence of ECG abnormalities was 17.6 [n = 95% confidence interval (CI) 15.0-20.1]. Prevalence of atrial fibrillation or prior myocardial infarction was 2.1% (95%CI 1.1-3.0) and of other ECG abnormalities related to increased cardiovascular disease risk 15.4% (95%CI 13.1-17.9). NNS to prevent one death from cardiovascular disease within 10 years was estimated at 260 (95%CI 220-308).

CONCLUSION

Our findings support the existing recommendations to routinely record an ECG in unselected hypertensive patients as the prevalence of relevant abnormalities is considerable and NNS to prevent one death is lower than that in other widely accepted tests.

Risk factors related to the occurrence of silent myocardial ischemia in Mexicans

BACKGROUND

Silent myocardial ischemia is a growing world health problem. It has been related to factors that promote an increase in myocardial oxygen demand or affect coronary vasomotor tone. Coronary artery disease has shown an increasing trend in Mexico in this century.

HYPOTHESIS

The aim of the study was to estimate the strength of the association between some risk factors and the occurrence of silent myocardial ischemia.

METHODS

A cross-sectional study was conducted and 249 individuals were screened by 24-h Holter electrocardiogram. Silent myocardial ischemia was diagnosed in patients with painless transient ST-segment depression. All subjects were interviewed for coronary risk factors and total serum cholesterol was measured.

RESULTS

Silent ischemia was diagnosed in 115 patients (46%), who were older (59 +/- 9 vs. 57 +/- 11 years; p = 0.01). In a logistic regression analysis, a lower risk for silent ischemia was found in patients with thrombolysis [odds ratio (OR) 0.28; 95% confidence interval (CI 95%) 0.14-0.53], or those who followed their medical treatment (OR 0.16; CI 95% 0.04-0.68). The major risk factors were hypercholesterolemia (OR 1.6; CI 95% 0.9-2.9) and more severe coronary artery disease (OR 2.5; CI 95% 1.1-5.7).

CONCLUSIONS

Some coronary risk factors are related to silent ischemia. It is still important to diagnose this entity, but modification of its related risk factors should be kept in mind to diminish its occurrence and its severe consequences.

Myocardial injury in critically ill patients: relation to increased cardiac troponin I and hospital mortality

OBJECTIVE

To examine the relationship between myocardial injury, assessed by cardiac troponin I (cTnI) levels, and outcome in selected critically ill patients without acute coronary syndromes or cardiac dysfunction.

DESIGN AND SETTING

Prospective, observational study in the emergency ICU of a university teaching hospital.

POPULATION

Over a 6-month period, 217 consecutive patients admitted to the ICU were studied.

METHODS AND RESULTS

cTnI assays were performed in all patients on admission to the ICU. The incidence of myocardial injury, defined by cTnI level > 0.1 ng/mL, was 32% (69 of 217 patients). Overall mortality was 27% (58 of 217 patients). Patients with myocardial injury had a mortality rate of 51%, compared with only 16% mortality for those without myocardial injury (p < 0.001). The hospital mortality rate was highest among older patients (71 +/- 14% vs 58.5 +/- 20%, p < 0.0001) and patients with higher simplified acute physiology scale (SAPS) II score (62 +/- 25% vs 37 +/- 17%, p < 0.0001). Mechanical ventilation was associated with higher in-hospital death (50% vs 31%, for patients who died in the hospital vs those who were discharged alive; p = 0.03). Elevated blood levels of cTnI were found to be independently associated with hospital mortality, regardless of the presence of SAPS II score and mechanical ventilation, in the logistic regression analysis (odds ratio, 2.09; 95% confidence interval, 1.06 to 4.11; p = 0.01).

CONCLUSIONS

This study demonstrates the high frequency of myocardial injury (32%) in critically ill patients without acute coronary syndromes or cardiac dysfunction on admission to ICU. Myocardial injury is an independent determinant of hospital mortality. Assessment of myocardial injury on admission to ICU would make it possible to identify patients at increased risk of death.

Clinical trial simulation using therapeutic effect modeling: application to ivabradine efficacy in patients with angina pectoris

Ivabradine is a new bradycardic agent with a potential indication for stable angina pectoris. To investigate the best compromise between efficacy, safety, drug regimen, and number of patients to include in a phase III study, we conducted Monte Carlo simulations using a full therapeutic model. The binary clinical outcome, chest pain, was simulated using a physiologic model in which the coronary reserve was derived from the heart rate. Safety was defined as being heart rate dependent. Using real data to build a pharmacokinetic-pharmacodynamic model controlling drug effect (i.e., heart rate decrease), and resampling heart rate profiles from the database, 100 clinical trials (N = 200) were simulated for five oral doses (2.5, 5, 10, 20, and 40 mg QD or BID) of ivabradine. Only 25% of the simulated trials showed a significant effect of ivabradine with doses up to 10 mg QD, and 48 and 55% of the trials with doses of 10 mg BID and 20 mg QD, respectively, and more than 80% of the trials with a 40 mg daily dose. For safety, 4% of patients had at least one adverse event in the untreated group, and from 5 to 13% in the treated groups for the lowest to the highest dose, respectively. The number of subjects to include in a future trial to obtain a 15% decrease in chest pain under the assumption of a 68% base risk, is 239 subjects per group with 10 mg BID or 196 with 20 mg QD. These results illustrate how clinical trial simulations including a PK/PD model as well as a physiopathologic mechanistic model, describing the relationship between the intermediate and clinical endpoint, and the resampling of real patients from a large database can help in designing future phase III trials.

Clinically recognized cardiac dysfunction: an independent determinant of mortality among critically ill patients. Is there a role for serial measurement of cardiac troponin I?

OBJECTIVE

To determine the relative importance of clinically recognized cardiac dysfunction and unrecognized cardiac injury to hospital mortality.

DESIGN

Prospective, blinded, single-center study.

SETTING

Medical ICU of Barnes-Jewish Hospital, St. Louis, a university-affiliated teaching hospital.

PATIENTS

Two hundred sixty adult patients requiring admission to the medical ICU.

INTERVENTIONS

Daily blood collection.

MAIN OUTCOME MEASURES

The presence of cardiac dysfunction (myocardial infarction, unstable angina, cardiac arrest, or congestive heart failure) as determined by the physicians responsible for the care of the patient. Daily measurement of levels of cardiac troponin I, a sensitive, highly specific, and long-lived marker of myocardial injury.

RESULTS

Fifty-five (21.2%) patients had clinical evidence of cardiac dysfunction, among whom 22 (40%) had an elevated level of cardiac troponin I. A total of 41 (15.8%) patients had evidence of acute myocardial injury based on elevated levels of cardiac troponin I. Patients with clinically recognized cardiac dysfunction had a significantly greater hospital mortality rate compared to patients without clinically recognized cardiac dysfunction (45.5% vs 10.2%; p < 0.001). Similarly, patients with elevated blood levels of cardiac troponin I had a greater hospital mortality rate compared to patients without elevated blood levels of cardiac troponin I (26.8% vs 16.0%; p = 0.095). Multiple logistic-regression analysis controlling for potential confounding variables demonstrated that the presence of clinically recognized cardiac dysfunction was independently associated with hospital mortality (adjusted odds ratio = 3.0; 95% confidence interval = 1.9 to 4.8; p = 0.016). However, having an elevated blood level of cardiac troponin I was not found to be an independent determinant of hospital mortality.

CONCLUSION

Among critically ill medical patients, clinically recognized cardiac dysfunction is an independent determinant of hospital mortality. The identification of unrecognized cardiac injury, using serial measurements of cardiac troponin I, did not independently contribute to the prediction of hospital mortality.