Diagnosing type 2 myocardial infarction in clinical routine. A validation study

Type 2 Myocardial Infarction-Poorly Understood, Underevaluated, and Too Often Ignored

This Viewpoint discusses diagnosis of type 2 myocardial infarction.

Application of the Universal Definition of Myocardial Infarction in Clinical Practice in Scotland and Sweden

Importance

Whether the diagnostic classifications proposed by the universal definition of myocardial infarction (MI) to identify type 1 MI due to atherothrombosis and type 2 MI due to myocardial oxygen supply-demand imbalance have been applied consistently in clinical practice is unknown.

Objective

To evaluate the application of the universal definition of MI in consecutive patients with possible MI across 2 health care systems.

Design, Setting, and Participants

This cohort study used data from 2 prospective cohorts enrolling consecutive patients with possible MI in Scotland (2013-2016) and Sweden (2011-2014) to assess accuracy of clinical diagnosis of MI recorded in hospital records for patients with an adjudicated diagnosis of type 1 or type 2 MI. Data were analyzed from August 2022 to February 2023.

Main Outcomes and Measures

The main outcome was the proportion of patients with a clinical diagnosis of MI recorded in the hospital records who had type 1 or type 2 MI, adjudicated by an independent panel according to the universal definition. Characteristics and risk of subsequent MI or cardiovascular death at 1 year were compared.

Results

A total of 50 356 patients were assessed. The cohort from Scotland included 28 783 (15 562 men [54%]; mean [SD] age, 60 [17] years), and the cohort from Sweden included 21 573 (11 110 men [51%]; mean [SD] age, 56 [17] years) patients. In Scotland, a clinical diagnosis of MI was recorded in 2506 of 3187 patients with an adjudicated diagnosis of type 1 MI (79%) and 122 of 716 patients with an adjudicated diagnosis of type 2 MI (17%). Similar findings were observed in Sweden, with 970 of 1111 patients with adjudicated diagnosis of type 1 MI (87%) and 57 of 251 patients with adjudicated diagnosis of type 2 MI (23%) receiving a clinical diagnosis of MI. Patients with an adjudicated diagnosis of type 1 MI without a clinical diagnosis were more likely to be women (eg, 336 women [49%] vs 909 women [36%] in Scotland; P < .001) and older (mean [SD] age, 71 [14] v 67 [14] years in Scotland, P < .001) and, when adjusting for competing risk from noncardiovascular death, were at similar or increased risk of subsequent MI or cardiovascular death compared with patients with a clinical diagnosis of MI (eg, 29% vs 18% in Scotland; P < .001).

Conclusions and Relevance

In this cohort study, the universal definition of MI was not consistently applied in clinical practice, with a minority of patients with type 2 MI identified, and type 1 MI underrecognized in women and older persons, suggesting uncertainty remains regarding the diagnostic criteria or value of the classification.

Impact of clinical diagnosis of myocardial infarction in patients with elevated cardiac troponin

OBJECTIVE

Type 2 myocardial infarction (MI) and myocardial injury are common conditions associated with an adverse prognosis. Physicians experience uncertainty how to distinguish these conditions, as well as how to manage and treat them. Therefore, the objective of this study was to compare treatment and prognosis in patients with an adjudicated diagnosis of type 2 MI and myocardial injury, who were discharged with and without a clinical diagnosis of MI.

DESIGN

The study consisted of two cohorts, 964 and 281 consecutive patients with elevated cardiac troponin, discharged with and without a clinical diagnosis of MI, respectively. All cases were adjudicated into MI type 1-5 or myocardial injury and followed regarding all-cause death.

RESULTS

The adjudication identified 138 and 37 cases of type 2 MI, and 86 and 185 of myocardial injury, with and without a clinical MI diagnosis, respectively. In patients with type 2 MI, a clinical MI diagnosis was associated with more coronary angiography investigations (39.1% vs 5.4%, p<0.001) and an increased use of secondary prevention medications (all p<0.001). However, no difference was observed in adjusted 5-year mortality between patients with and without a clinical MI diagnosis (HR: 0.77 with 95% CI 0.43 to 1.38). The results were similar for adjudicated myocardial injury.

CONCLUSION

In both type 2 MI and myocardial injury, a clinical diagnosis of MI at discharge was associated with more investigations and treatments. However, no prognostic effect of receiving a clinical MI diagnosis was observed.

A new clinical classification of acute myocardial infarction

The existence of a universal definition of myocardial infarction-which involves classification into multiple subtypes-has promoted the use of standard diagnostic criteria across the world. However, this classification has not been applied consistently in practice and is perceived by some as too complicated. Where there is diagnostic uncertainty, patients have worse outcomes. This uncertainty has also impacted on the validity of the diagnosis of myocardial infarction in clinical trials. To address these issues and to encourage clinicians to recognize that different mechanisms of myocardial infarction have differing treatment implications, we propose an alternative clinical classification for consideration; one that recognizes that myocardial infarction can arise spontaneously, secondary to another condition, or as a complication of a cardiac procedure. This classification is aligned with clinical practice and proposes more objective and specific diagnostic criteria that, if agreed by international consensus, could reduce diagnostic uncertainty in practice and research.

Management and outcome trends in type 2 myocardial infarction: an investigation from the SWEDEHEART registry

Despite poor prognosis, patients with type 2 myocardial infarction (MI) tend to be underdiagnosed and undertreated compared to those with type 1 MI. Whether this discrepancy has improved over time is uncertain. We conducted a registry-based cohort study investigating type 2 MI patients managed at Swedish coronary care units (n = 14,833) during 2010-2022. Multivariable-adjusted changes (first three vs last three calendar years of the observation period) were assessed regarding diagnostic examinations (echocardiography, coronary assessment), provision of cardioprotective medications (betablockers, renin-angiotensin-aldosterone-system inhibitors, statins) and 1-year all-cause mortality. Compared to type 1 MI patients (n = 184,329), those with type 2 MI less often had diagnostic examinations and cardioprotective medications. Increases in the use of echocardiography (OR 1.08 [95% confidence interval 1.06-1.09]) and coronary assessment (OR 1.06 [95% confidence interval 1.04-1.08]) were smaller compared to type 1 MI (p_interaction < 0.001). The provision of medications did not increase in type 2 MI. All-cause mortality rate in type 2 MI was 25.4% without temporal change (OR 1.03 [95% confidence interval 0.98-1.07]). Taken together, the provision of medications and all-cause mortality did ot improve in type 2 MI despite modest increases in diagnostic procedures. This emphasizes the need of defining optimal care pathways in these patients.

Clinical and prognostic implications of high-sensitivity cardiac troponin T concentrations in type 2 non-ST elevation myocardial infarction

Background

While the clinical importance of cardiac troponin is well-known in type 1 myocardial infarction (MI), evidence on this topic in type 2 MI is limited. We assessed the clinical and prognostic implications of high-sensitivity cardiac troponin (hs-cTnT) concentrations in a large sample of patients with type 2 MI.

Methods

Retrospective registry-based cohort study (SWEDEHEART) including 4607 patients with type 2 MI and 43,405 patients with type 1 MI, used for comparisons. Patients with ST-elevation MI were excluded. Multivariable-adjusted regressions were applied to investigate the associations of hs-cTnT concentrations (highest measured value during each hospitalization) with clinical variables and prognosis during a median follow-up of up to 1.9 years.

Results

Hs-cTnT concentrations (median 264 [25th, 75th percentiles 112–654] ng/L) were significantly associated with various cardiovascular risk factors and comorbidities in type 2 non-ST elevation MI (NSTEMI) but only weakly with the underlying triggering condition. Most of these findings including the magnitude of hs-cTn release were similar to type 1 NSTEMI. Hs-cTnT (ln) independently predicted all-cause mortality (hazard ratio 1.13 [95% confidence interval 1.09–1.17]) and major adverse events (hazard ratio 1.13 [95% confidence interval 1.10–1.17]) in type 2 NSTEMI, similar as for type 1 NSTEMI according to interaction analysis. The associations of hs-cTnT (ln) with poor prognosis tended to be stronger in type 2 NSTEMI patients without known cardiovascular disease.

Conclusions

Hs-cTnT concentrations independently predict adverse outcome in type 2 NSTEMI. The similarities to type 1 NSTEMI however, are striking and emphasize the difficulty to distinguish both MI types.

The Intersection of Type 2 Myocardial Infarction and Heart Failure

Background

Type 2 myocardial infarction (T2MI) is common and associated with high cardiovascular event rates. However, the relationship between T2MI and heart failure (HF) is uncertain.

Methods and Results

We identified patients with T2MI at a large tertiary hospital between October 2017 and May 2018. Patient characteristics, causes of T2MI, and subsequent HF hospitalizations were determined by physician chart review. We identified 359 patients with T2MI over the study period; 184 patients had a history of HF. Among patients with ejection fraction (EF) assessment (N=180), the majority had preserved EF (N=107; 59.4%), followed by reduced EF (N=54; 30.0%), and mid‐range EF (N=19; 10.6%). Acute HF was the most common cause of T2MI (20.9%). Of those whose T2MI was precipitated by HF (N=75), the mean EF was 53.0±16.8% and 16 (21.3%) were de novo diagnoses of HF. Among patients with T2MI who were discharged alive with available follow‐up (N=289), 5.5% were hospitalized with acute HF within 30 days, 17.3% within 180 days, and 22.1% within 1 year. In subgroup analyses, among patients with T2MI with prevalent or new HF (N=161), the rate of HF hospitalization at 1 year was 34.2%, considerably higher than those with T2MI and no HF diagnosis at discharge (7.0%; N=9/128).

Conclusions

Index presentations of HF or worsening chronic HF represent the most common causes of T2MI. ≈1 in 5 patients with T2MI will be readmitted for HF within 1 year of their event. Strategies to prevent HF events after a T2MI are needed.

Sex differences in investigations and outcomes among patients with type 2 myocardial infarction

OBJECTIVES

Type 2 myocardial infarction (MI) is a heterogenous condition and whether there are differences between women and men is unknown. We evaluated sex differences in clinical characteristics, investigations and outcomes in patients with type 2 MI.

METHODS

In the Swedish Web based system for Enhancement and Development of Evidence based care in Heart disease Evaluated According to Recommended Therapies (SWEDEHEART) registry, we compared patients admitted to coronary care units with a diagnosis of type 1 or type 2 MI. Sex-stratified Cox regression models evaluated the association with all-cause death in men and women separately.

RESULTS

We included 57 264 (median age 73 years, 65% men) and 6485 (median age 78 years, 50% men) patients with type 1 and type 2 MI, respectively. No differences were observed in the proportion of men and women with type 2 MI who underwent echocardiography and coronary angiography, but women were less likely than men to have left ventricular (LV) impairment and obstructive coronary artery disease (CAD). Compared with type 1 MI, patients with type 2 MI had higher risk of death regardless of sex (men: adjusted HR 1.55 (95% CI 1.44 to 1.67); women: adjusted HR 1.34 (95% CI 1.24 to 1.45)). In those with type 2 MI, the risk of death was lower for women than men (adjusted HR 0.85 (95% CI 0.76 to 0.92) (men, reference)).

CONCLUSIONS

Type 2 MI occurred in men and women equally and we found no evidence of sex bias in the selection of patients for cardiac investigations. Patients with type 2 MI had worse outcomes, but women were less likely to have obstructive CAD or severe LV impairment and were more likely to survive than men.

Validation of myocardial infarction diagnosis in patients with congenital heart disease in Sweden

Background

The population of adults with congenital heart disease (CHD) is growing, and increasingly more patients with CHD reach older ages. Patients with CHD are at an increased risk of myocardial infarction (MI) with increased age. Diagnosing MI in patients with CHD can be challenging in clinical practice owing to a high prevalence of aberrant electrocardiograms, ventricular hypertrophy, and heart failure, among other factors. The National Swedish Patient Register (NPR) is widely used in epidemiological studies; however, MI diagnoses specifically in patients with CHD have never been validated in the NPR.

Methods

We contacted hospitals and medical archive services to request medical records for 249 patients, born during 1970–2012, with both CHD and MI diagnoses and who were randomly selected from the NPR by the Swedish National Board of Health and Welfare. Follow-up was until 2015. We performed a medical chart review to validate the MI diagnoses; we also validated CHD diagnoses to ensure that only patients with confirmed CHD diagnoses were included in the MI validation process.

Results

We received medical records for 96.4% (n = 238/249) of patients for validation of CHD diagnoses. In total, 74.8% (n = 178/238) had a confirmed CHD diagnosis; of these, 70.2% (n = 167) had a fully correct CHD diagnosis in the NPR; a further 4.6% (n = 11) had a CHD diagnosis, but it was misclassified. MI diagnoses were validated in 167 (93.8%) patients with confirmed CHD. Of the patients with confirmed CHD, 88.0% (n = 147/167) had correct MI diagnoses. Patients with non-complex CHD diagnoses had more correct MI diagnoses than patients with complex CHD (91.0%, n = 131 compared with 69.6%, n = 16). The main cause for incorrect MI diagnoses was typographical error, contributing to 50.0% of the incorrect diagnoses.

Conclusions

The validity of MI diagnoses in patients with confirmed CHD in the NPR is high, with nearly 9 of 10 MI diagnoses being correct (88.0%). MI in patients with CHD can safely be studied using the NPR.