Association Between Silent Myocardial Infarction and Long-Term Risk of Sudden Cardiac Death

Burden of risk factors in women and men with unrecognized myocardial infarction: a systematic review and meta-analysis †

Unrecognized myocardial infarction (MI) is an MI that remains undetected in the acute phase and is associated with an unfavourable prognosis. With this systematic review and meta-analysis, we evaluated the burden of cardiovascular risk factors in individuals with unrecognized MI. We searched general population-based cohort studies diagnosing unrecognized MI by electrocardiogram or myocardial imaging up to 24 November 2023. Pooled mean differences (MDs) or risk ratios (RRs) with 95% confidence intervals (CIs) were determined, and random-effects meta-analyses were performed. Fourteen cohort studies were included involving 200 450 individuals (mean age 62.8 ± 9.9 years, 56.0% women), among which 4322 (2.2%) experienced unrecognized MI (mean age 66.3 ± 8.2 years, 47.8% women) and 4653 (2.1%) recognized MI (mean age 68.5 ± 7.3 years, 33.8% women). Compared to individuals without MI, those with unrecognized MI had higher body mass index (MD 0.27, 95% CI 0.16-0.39) and systolic blood pressure (MD 4.48, 95% CI 2.81-6.15) levels, and higher prevalence of hypertension (RR 1.27, 95% CI 1.06-1.51) and diabetes mellitus (RR 1.67, 95% CI 1.36-2.06). Furthermore, individuals with unrecognized MI had lower prevalence of hypertension (RR 0.92, 95% CI 0.88-0.97) and diabetes mellitus (RR 0.80, 95% CI 0.70-0.92). Individuals with unrecognized MI are characterized by a substantial burden of metabolic risk factors. Our findings suggest insufficient recognition and management of cardiovascular risk factors among individuals with unrecognized MI.

Longitudinal blood glucose level and increased silent myocardial infarction: a pooled analysis of four cohort studies

BACKGROUND

Fasting glucose (FG) demonstrates dynamic fluctuations over time and is associated with cardiovascular outcomes, yet current research is limited by small sample sizes and relies solely on baseline glycemic levels. Our research aims to investigate the longitudinal association between FG and silent myocardial infarction (SMI) and also delves into the nuanced aspect of dose response in a large pooled dataset of four cohort studies.

METHODS

We analyzed data from 24,732 individuals from four prospective cohort studies who were free of myocardial infarction history at baseline. We calculated average FG and intra-individual FG variability (coefficient of variation), while SMI cases were identified using 12-lead ECG exams with the Minnesota codes and medical history. FG was measured for each subject during the study's follow-up period. We applied a Cox regression model with time-dependent variables to assess the association between FG and SMI with adjustment for age, gender, race, Study, smoking, longitudinal BMI, low-density lipoprotein level, blood pressure, and serum creatinine.

RESULTS

The average mean age of the study population was 60.5 (sd: 10.3) years with median fasting glucose of 97.3 mg/dL at baseline. During an average of 9 years of follow-up, 357 SMI events were observed (incidence rate, 1.3 per 1000 person-years). The association between FG and SMI was linear and each 25 mg/dL increment in FG was associated with a 15% increase in the risk of SMI. This association remained significant after adjusting for the use of lipid-lowering medication, antihypertensive medication, antidiabetic medication, and insulin treatment (HR 1.08, 95% CI 1.01-1.16). Higher average FG (HR per 25 mg/dL increase: 1.17, 95% CI 1.08-1.26) and variability of FG (HR per 1 sd increase: 1.23, 95% CI 1.12-1.34) over visits were also correlated with increased SMI risk.

CONCLUSIONS

Higher longitudinal FG and larger intra-individual variability in FG over time were associated in a dose-response manner with a higher SMI risk. These findings support the significance of routine cardiac screening for subjects with elevated FG, with and without diabetes.

Association between Blood Lead Levels and Silent Myocardial Infarction in the General Population

Background: Although the link between lead exposure and patterns of cardiovascular disease (CVD) has been reported, its association with silent myocardial infarction (SMI) remains unexplored. We aimed to assess the association between blood lead levels (BLLs) and SMI risk. Methods: We included 7283 (mean age 56.1 ± 2.52 years, 52.5% women) participants free of CVD from the Third National Health and Nutrition Examination Survey. BLL was measured using graphite-furnace atomic absorption spectrophotometry. SMI was defined as ECG evidence of myocardial infarction (MI) without history of MI. The association between SMI and BLLs was examined using multivariable logistic regression. Results: SMI was detected in 120 participants with an unweighted prevalence of 1.65%. Higher BLL correlated with higher SMI prevalence across BLL tertiles. In multivariable-adjusted models, participants in the third BLL tertile had more than double the odds of SMI (OR: 3.42, 95%CI: 1.76-6.63) compared to the first tertile. Each 1 µg/dL increase in BLL was linked to a 9% increase in SMI risk. This association was consistent across age, sex, and race subgroups. Conclusions: Higher BLLs are associated with higher odds of SMI in the general population. These results underscore the significance of the ongoing efforts to mitigate lead exposure and implement screening strategies for SMI in high-risk populations.

Silent Myocardial Ischemia: From Pathophysiology to Diagnosis and Treatment

Silent myocardial ischemia (SMI), characterized by a lack of overt symptoms despite an inadequate blood supply to the myocardium, remains a challenging entity in cardiovascular medicine. The pathogenesis involves intricate interactions of vascular, neurohormonal, and metabolic factors, contributing to perfusion deficits without the characteristic chest pain. Understanding these mechanisms is pivotal for recognizing diverse clinical presentations and designing targeted interventions. Diagnostic strategies for SMI have evolved from traditional electrocardiography to advanced imaging modalities, including stress echocardiography, single-photon emission computed tomography (SPECT), positron emission tomography (PET), and cardiac magnetic resonance imaging (MRI). Treating SMI is a matter of ongoing debate, as the available evidence on the role of invasive versus medical management is controversial. This comprehensive review synthesizes current knowledge of silent myocardial ischemia, addressing its pathophysiology, diagnostic modalities, and therapeutic interventions.

Silent Myocardial Ischemia Revisited, Another Silent Killer, Emphasis on the Diagnostic Value of Stress Echocardiography with Focused Update and Review

Silent myocardial ischemia (SMI) is a relatively common phenomenon in patients with coronary artery disease (CAD). The original description of SMI dates back to the 1970s. We performed an extensive search of the literature starting from 2000, using MEDLINE or PubMed, and 676 documents were analyzed, and only 45 articles found suitable for the study were selected. Data regarding the prevalence and risk factors of SMI were discussed, along with the different mechanistic processes behind it; also, methods for screening and diagnosis are exposed, namely electrocardiographic stress test, stress echocardiography, and single-photon emission computed tomography (SPECT). The silent nature of the condition presumes that patients are diagnosed at a more advanced stage, and screening high-risk patients for early management is essential. Education of patients is necessary, and medical management along with cardiac rehabilitation is valid for mild cases, whereas patients with moderate-to-severe myocardial ischemia might require a more invasive approach. SMI is relatively common, diagnostic approach offers data regarding the presence of ischemia along with its anatomic extent, providing important prognostic value. Given its silent and critical nature, future directions for better screening and management must be searched and implemented extensively.

Dynamic Change of Cardiovascular Health Metrics and Long‐Term Risk of Sudden Cardiac Death: The ARIC Study

Background

The change of cardiovascular health (CVH) status has been associated with risk of cardiovascular disease. However, no studies have explored the change patterns of CVH in relation to risk of sudden cardiac death (SCD). We aim to examine the link between baseline CVH and change of CVH over time with the risk of SCD.

Methods and Results

Analyses were conducted in the prospective cohort ARIC (Atherosclerosis Risk in Communities) study, started in 1987 to 1989. ARIC enrolled 15 792 individuals 45 to 64 years of age from 4 US communities (Forsyth County, North Carolina; Jackson, Mississippi; suburbs of Minneapolis, Minnesota; and Washington County, Maryland). Subjects with 0 to 2, 3 to 4, and 5 to 7 ideal metrics of CVH were categorized as having poor, intermediate, or ideal CVH, respectively. Change in CVH over 6 years between 1987 to 1989 and 1993 to 1995 was considered. The primary study outcome was physician adjudicated SCD. The study population consisted of 15 026 subjects, of whom 12 207 had data about CVH change. Over a median follow‐up of 23.0 years, 583 cases of SCD were recorded. There was a strong inverse association between baseline CVH metrics and time varying CVH metrics with risk of SCD. Compared with subjects with consistently poor CVH, risk of SCD was lower in those changed from poor to intermediate/ideal (hazard ratio [HR], 0.67 [95% CI, 0.48–0.94]), intermediate to poor (HR, 0.73 [95% CI, 0.54–0.99]), intermediate to ideal (HR, 0.49 [95% CI, 0.24–0.99]), ideal to poor/intermediate CVH (HR, 0.23 [95% CI, 0.10–0.52]), or those with consistently intermediate (HR, 0.49 [95% CI, 0.36–0.66]) or consistently ideal CVH (HR, 0.31 [95% CI, 0.13–0.76]). Similar results were also observed for non‐SCD.

Conclusions

Compared with consistently poor CVH, other patterns of change in CVH were associated with lower risk of SCD. These findings highlight the importance of promotion of ideal CVH in the primordial prevention of SCD.

Risk factors for sudden cardiac arrest in patients with ST-segment elevation myocardial infarction: a retrospective cohort study

Background

Sudden cardiac arrest (SCA) is a critical complication of acute myocardial infarction, especially ST-segment elevation myocardial infarction (STEMI). This study identified the risk factors for SCA in patients with STEMI before receiving catheterization.

Methods

We retrospectively analyzed the data of patients with STEMI and cardiac arrest who presented to a tertiary care center in Taiwan between January 1, 2016, and December 31, 2019. Only patients with coronary artery disease (CAD) confirmed by coronary angiography were included in this study. We collected the patients’ demographic and clinical data, such as age, sex, medical history, estimated glomerular filtration rate (eGFR), and coronary angiographic findings. The primary outcome of this study was SCA in patients with STEMI. Continuous and nominal variables were compared using the two-sample Student's t-test and chi-squared test, respectively. The results of logistic regression were subjected to multivariate analysis with adjustment for possible confounders.

Results

A total of 920 patients with STEMI and coronary angiography–documented CAD and 108 patients with SCA who presented between January 1, 2016, and December 31, 2019, were included. The bivariate logistic regression analysis of patients’ demographic data revealed that patients with STEMI and SCA were slightly younger, were more likely to have diabetes mellitus, and had a lower eGFR than did the patients without SCA. The coronary angiographic findings indicated a higher prevalence of left main CAD and three-vessel disease in patients with SCA than in patients without SCA. Multivariate logistic regression revealed that left main CAD (odds ratio [OR]: 3.77; 95% confidence interval [CI], 1.84 to 7.72), a lower eGFR (OR: 0.97; 95% CI, 0.96 to 0.98), and younger age (OR: 0.98; 95% CI, 0.96 to 0.99) were the risk factors for SCA in patients with STEMI.

Conclusions

Left main CAD, lower eGFR, and younger age are the risk factors for cardiac arrest in patients with acute myocardial infarction.

Association Between Temporal Changes in Early Repolarization Pattern With Long-Term Cardiovascular Outcome: A Population-Based Cohort Study

Background

The prognostic value of early repolarization pattern (ERP) remains controversial. We aim to test the hypothesis that temporal changes in ERP are associated with increased risks for sudden cardiac death (SCD) and cardiovascular death.

Methods and Results

A total of 14 679 middle‐aged participants from the prospective, population‐based cohort were included in this analysis, with ERP status recorded at baseline and during 3 follow‐up visits in the ARIC (Atherosclerosis Risk in Communities) study. We related baseline ERP, time‐varying ERP, and temporal changes in ERP to cardiovascular outcomes. Cox models were used to estimate the hazard ratios (HRs) adjusted for possible confounding factors. With a median follow‐up of 22.5 years, there were 5033 deaths, 1239 cardiovascular deaths, and 571 SCDs. Time‐varying ERP was associated with increased risks of SCD (HR, 1.59 [95% CI, 1.25–2.02]), cardiovascular death (HR, 1.70 [95% CI, 1.44–2.00]), and death from any cause (HR, 1.16 [95% CI, 1.05–1.27]). Baseline ERP was also associated with 3 outcomes. Compared with those with consistently normal ECG findings, subjects with new‐onset ERP or consistent ERP experienced increased risks of developing SCD and cardiovascular death. The time‐varying ERP in women, White subjects, and anterior leads and J‐wave amplitudes ≥0.2 mV appeared to indicate poorer cardiovascular outcomes.

Conclusions

Our findings suggest that baseline ERP, time‐varying ERP, new‐onset ERP, and consistent ERP were independent predictors of SCD and cardiovascular death in the middle‐aged biracial population. Repeated measurements of the ERP might improve its use as a risk indicator for SCD.

Association Between Dynamic Change of QT Interval and Long-Term Cardiovascular Outcomes: A Prospective Cohort Study

Background: The prolongation or shortening of heart rate-corrected QT (QTc) predisposes patients to fatal ventricular arrhythmias and sudden cardiac death (SCD), but the association of dynamic change of QTc interval with mortality in the general population remains unclear.

Methods: A total of 11,798 middle-aged subjects from the prospective, population-based cohort were included in this analysis. The QTc interval corrected for heart rate was measured on two occasions around 3 years apart in the Atherosclerosis Risk in Communities (ARIC) study. The ΔQTc interval was calculated by evaluating a change in QTc interval from visit 1 to visit 2.

Results: After a median follow-up of 19.5 years, the association between the dynamic change of QTc interval and endpoints of death was U-shaped. The multivariate-adjusted hazard ratios (HRs) comparing subjects above the 95th percentile of Framingham–corrected ΔQTc (ΔQTcF) (≥32 ms) with subjects in the middle quintile (0–8 ms) were 2.69 (95% CI, 1.68–4.30) for SCD, 2.51 (1.68–3.74) for coronary heart disease death, 2.10 (1.50–2.94) for cardiovascular death, and 1.30 (1.11–1.55) for death from any cause. The corresponding HRs comparing subjects with a ΔQTcF below the fifth percentile (<-23 ms) with those in the middle quintile were 1.82 (1.09–3.05) for SCD, 1.83 (1.19–2.81) for coronary heart disease death, 2.14 (1.51–2.96) for cardiovascular death, and 1.31 (1.11–1.56) for death from any cause. Less extreme deviations of ΔQTcF were also associated with an increased risk of death. Similar, albeit weaker associations also were observed with ΔQTc corrected with Bazett's formula.

Conclusions: A dynamic change of QTc interval is associated with increased mortality risk in the general population, indicating that repeated measurements of the QTc interval may be available to provide additional prognostic information.

Airflow obstruction, impaired lung function and risk of sudden cardiac death: a prospective cohort study

BACKGROUND

Growing evidence suggests that compromised lung health may be linked to cardiovascular disease. However, little is known about its association with sudden cardiac death (SCD).

OBJECTIVES

We aimed to assess the link between impaired lung function, airflow obstruction and risk of SCD by race and gender in four US communities.

METHODS

A total of 14 708 Atherosclerosis Risk in Communities (ARIC) study participants who underwent spirometry and were asked about lung health (1987-1989) were followed. The main outcome was physician-adjudicated SCD. Fine-Gray proportional subdistribution hazard models with Firth's penalised partial likelihood correction were used to estimate the HRs.

RESULTS

Over a median follow-up of 25.4 years, 706 (4.8%) subjects experienced SCD. The incidence of SCD was inversely associated with FEV₁ in each of the four race and gender groups and across all smoking status categories. After adjusting for multiple measured confounders, HRs of SCD comparing the lowest with the highest quintile of FEV₁ were 2.62 (95% CI 1.62 to 4.26) for white males, 1.80 (95% CI 1.03 to 3.15) for white females, 2.07 (95% CI 1.05 to 4.11) for black males and 2.62 (95% CI 1.21 to 5.65) for black females. The above associations were consistently observed among the never smokers. Moderate to very severe airflow obstruction was associated with increased risk of SCD. Addition of FEV₁ significantly improved the predictive power for SCD.

CONCLUSIONS

Impaired lung function and airflow obstruction were associated with increased risk of SCD in general population. Additional research to elucidate the underlying mechanisms is warranted.

Silent Myocardial Infarction and Subsequent Ischemic Stroke in the Cardiovascular Health Study

OBJECTIVE

To test the hypothesis that silent myocardial infarction (MI) is a risk factor for ischemic stroke, we evaluated the association between silent MI and subsequent ischemic stroke in the Cardiovascular Health Study.

METHODS

The Cardiovascular Health Study prospectively enrolled community-dwelling individuals ≥65 years of age. We included participants without prevalent stroke or baseline evidence of MI. Our exposures were silent and clinically apparent, overt MI. Silent MI was defined as new evidence of Q-wave MI, without clinical symptoms of MI, on ECGs performed during annual study visits from 1989 to 1999. The primary outcome was incident ischemic stroke. Secondary outcomes were ischemic stroke subtypes: nonlacunar, lacunar, and other/unknown. Cox proportional hazards analysis was used to model the association between time-varying MI status (silent, overt, or no MI) and stroke after adjustment for baseline demographics and vascular risk factors.

RESULTS

Among 4,224 participants, 362 (8.6%) had an incident silent MI, 421 (10.0%) an incident overt MI, and 377 (8.9%) an incident ischemic stroke during a median follow-up of 9.8 years. After adjustment for demographics and comorbidities, silent MI was independently associated with subsequent ischemic stroke (hazard ratio [HR], 1.51; 95% confidence interval [CI], 1.03-2.21). Overt MI was associated with ischemic stroke both in the short term (HR, 80; 95% CI, 53-119) and long term (HR, 1.60; 95% CI, 1.04-2.44). In secondary analyses, the association between silent MI and stroke was limited to nonlacunar ischemic stroke (HR, 2.40; 95% CI, 1.36-4.22).

CONCLUSION

In a community-based sample, we found an association between silent MI and ischemic stroke.

Silent Myocardial Infarction and Long-Term Risk of Frailty: The Atherosclerosis Risk in Communities Study

Background

Silent myocardial infarction (SMI) accounts for more than half of all MIs, and common risk factors and pathophysiological pathways coexist between SMI and frailty. The risk of frailty among patients with SMI is not well established. This study aimed to examine the association between SMI and frailty.

Methods and Results

This analysis included data from the Atherosclerosis Risk in Communities study. Patients without MI at baseline were eligible for inclusion. SMI was defined as electrocardiographic evidence of MI without clinical MI (CMI) after the baseline and until the fourth visit. Frailty was assessed during the fifth visit. A total of 4953 participants were included with an average age of 52.2±5.1 years. Among these participants, 2.7% (n=135) developed SMI, and 2.9% (n=146) developed CMI. After a median follow-up time of 14.7 (14.0–15.3) years, 6.7% (n=336) of the participants developed frailty. Patients with SMI and CMI were significantly more likely to become frail than those without MI (15.6% vs 6.2%, P<0.001 and 16.4% vs 6.2%, P<0.001, respectively). After adjusting for confounders, SMI and CMI were found to be independent predictors of frailty (odds ratio [OR]=2.243, 95% confidence interval [CI]=1.307–3.850, P=0.003 and OR=2.164, 95% CI=1.259–3.721, P=0.005, respectively). The association was consistent among the subgroups of age, sex, race, diabetes, and hypertension.

Conclusion

In conclusion, both SMI and CMI were found to be associated with a higher risk of frailty. Future studies are needed to confirm the beneficial effects of screening for SMI as well as to implement standardized preventive treatment to reduce the risk of frailty.

Clinical Trial Registration

URL: https://www.clinicaltrials.gov; Unique identifier: NCT00005131.

Association Between Silent Myocardial Infarction and Long-Term Risk of Sudden Cardiac Death

Background Although silent myocardial infarction (SMI) is prognostically important, the risk of sudden cardiac death (SCD) among patients with incident SMI is not well established. Methods and Results We examined 2 community-based cohorts: the ARIC (Atherosclerosis Risk in Communities) study (n=13 725) and the CHS (Cardiovascular Health Study) (n=5207). Incident SMI was defined as electrocardiographic evidence of new myocardial infarction during follow-up visits that was not present at the baseline. The primary study end point was physician-adjudicated SCD. In the ARIC study, 513 SMIs, 441 clinically recognized myocardial infarctions (CMIs), and 527 SCD events occurred during a median follow-up of 25.4 years. The multivariable hazard ratios of SMI and CMI for SCD were 5.20 (95% CI, 3.81-7.10) and 3.80 (95% CI, 2.76-5.23), respectively. In the CHS, 1070 SMIs, 632 CMIs, and 526 SCD events occurred during a median follow-up of 12.1 years. The multivariable hazard ratios of SMI and CMI for SCD were 1.70 (95% CI, 1.32-2.19) and 4.08 (95% CI, 3.29-5.06), respectively. The pooled hazard ratios of SMI and CMI for SCD were 2.65 (2.18-3.23) and 3.99 (3.34-4.77), respectively. The risk of SCD associated with SMI is stronger with White individuals, men, and younger age. The population-attributable fraction of SCD was 11.1% for SMI, and SMI was associated with an absolute risk increase of 8.9 SCDs per 1000 person-years. Addition of SMI significantly improved the predictive power for both SCD and non-SCD. Conclusions Incident SMI is independently associated with an increased risk of SCD in the general population. Additional research should address screening for SMI and the role of standard post-myocardial infarction therapy.