Comparison of Troponin Elevation, Prior Myocardial Infarction, and Chest Pain in Acute Ischemic Heart Failure

Using fractional polynomials and restricted cubic splines to model non-proportional hazards or time-varying covariate effects in the Cox regression model

The Cox proportional hazards model is used extensively in clinical and epidemiological research. A key assumption of this model is that of proportional hazards. A variable satisfies the proportional hazards assumption if the effect of that variable on the hazard function is constant over time. When the proportional hazards assumption is violated for a given variable, a common approach is to modify the model so that the regression coefficient associated with the given variable is assumed to be a linear function of time (or of log‐time), rather than being constant or fixed. However, this is an unnecessarily restrictive assumption. We describe two different methods to allow a regression coefficient, and thus the hazard ratio, in a Cox model to vary as a flexible function of time. These methods use either fractional polynomials or restricted cubic splines to model the log‐hazard ratio as a function of time. We illustrate the utility of these methods using data on 12 705 patients who presented to a hospital emergency department with a primary diagnosis of heart failure. We used a Cox model to assess the association between elevated cardiac troponin at presentation and the hazard of death after adjustment for an extensive set of covariates. SAS code for implementing the restricted cubic spline approach is provided, while an existing Stata function allows for the use of fractional polynomials.

Early invasive coronary angiography and acute ischaemic heart failure outcomes

Aims 

While myocardial ischaemia plays a major role in the pathogenesis of heart failure (HF), the indications for coronary angiography during acute HF are not established. We determined the association of early coronary angiography during acute HF hospitalization with 2-year mortality, cardiovascular death, HF readmissions, and coronary revascularization.

Methods and results 

In a two-stage sampling process, we identified acute HF patients who presented to 70 emergency departments in Ontario (April 2010 to March 2013) and determined whether they underwent early coronary angiography within 14 days after presentation using administrative databases. After clinical record review, we defined a cohort with acute ischaemic HF as patients with at least one factor suggesting underlying ischaemic heart disease, including previous myocardial infarction, troponin elevation, or angina on presentation. We oversampled patients undergoing angiography. We used inverse-probability-of-treatment weighting (IPTW) to adjust for baseline differences. Of 7239 patients with acute HF, 2994 met inclusion criteria [median age 75 (interquartile range 65–83) years; 40.9% women]. Early angiography was performed in 1567 patients (52.3%) and was associated with lower all-cause mortality [hazard ratio (HR) 0.74, 95% confidence interval (CI) 0.61–0.90, P = 0.002], cardiovascular death (HR 0.72, 95% CI 0.56–0.93, P = 0.012), and HF readmissions (HR 0.84, 95% CI 0.71–0.99, P = 0.042) after IPTW. Those undergoing early angiography experienced higher rates of percutaneous coronary intervention (HR 2.58, 95% CI 1.73–3.86, P < 0.001) and coronary artery bypass grafting (HR 2.94, 95% CI 1.75–4.93, P < 0.001) within 2 years.

Conclusions 

Early coronary angiography was associated with lower all-cause mortality, cardiovascular death, HF readmissions, and higher rates of coronary revascularization in acute HF patients with possible ischaemia.

Intensity of Guideline-Directed Medical Therapy for Coronary Heart Disease and Ischemic Heart Failure Outcomes

PURPOSE

The impact of guideline-directed medical therapy for coronary heart disease in those hospitalized with acute heart failure is unknown.

METHODS

We studied guideline-directed medical therapies for coronary disease: angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs), beta-adrenoreceptor antagonists, antiplatelet agents or anticoagulants, and statins. Using inverse probability of treatment weighting the propensity score, we examined associations of guideline-directed medical therapy intensity (categorized as low [0-1], high [2-3], or very high [4] number of drugs) with mortality in 1873 patients with angina, troponin elevation, or prior myocardial infarction.

RESULTS

At discharge, 0-1, 2-3, and 4 medications were prescribed in 467 (25%), 705 (38%), and 701 (37%) patients, respectively. Relative to those prescribed 0-1 drugs (reference), all-cause mortality was lower with 2-3 (hazard ratio [HR] 0.48, 95% confidence interval [CI] 0.28-0.84, P = 0.009) or all 4 drug classes (HR 0.56, 95% CI 0.33-0.96, P = 0.034) over 181-365 days, with similar reductions present from 0-180 days. In those with heart failure with preserved ejection fraction, mortality trended lower with 2-3 drug classes (HR 0.43, 95% CI 0.18-1.02, P = 0.054) and was significantly reduced with 4 drugs (HR 0.32, 95%CI 0.12-0.84, P = 0.021) during 0-180 day follow-up. In heart failure with reduced ejection fraction, all-cause mortality was reduced during both 0-180 and 181-365 days when discharged on 2-3 (HR 0.30 for 181-365 days, 95%CI 0.14-0.64, P = 0.002) or all 4 drug classes (HR 0.43, 95%CI 0.19-0.95, P = 0.038).

CONCLUSIONS

Increasing guideline-directed medical therapy intensity for coronary heart disease resulted in lower mortality in patients with acute ischemic heart failure with both preserved and reduced ejection fractions.

Cardiac Troponin Testing in Patients with COVID-19: A Strategy for Testing and Reporting Results

BACKGROUND

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that emerged late in 2019 causing COVID-19 (coronavirus disease-2019) may adversely affect the cardiovascular system. Publications from Asia, Europe, and North America have identified cardiac troponin as an important prognostic indicator for patients hospitalized with COVID-19. We recognized from publications within the first 6 months of the pandemic that there has been much uncertainty on the reporting, interpretation, and pathophysiology of an increased cardiac troponin concentration in this setting.

CONTENT

The purpose of this mini-review is: a) to review the pathophysiology of SARS-CoV-2 and the cardiovascular system, b) to overview the strengths and weaknesses of selected studies evaluating cardiac troponin in patients with COVID-19, and c) to recommend testing strategies in the acute period, in the convalescence period and in long-term care for patients who have become ill with COVID-19.

SUMMARY

This review provides important educational information and identifies gaps in understanding the role of cardiac troponin and COVID-19. Future, properly designed studies will hopefully provide the much-needed evidence on the path forward in testing cardiac troponin in patients with COVID-19.