Difference in the in-hospital prognosis between ST-segment elevation myocardial infarction and non-ST-segment elevation myocardial infarction with high Killip class: Data from the Japan Acute Myocardial Infarction Registry

Abstract

Background

ST-segment elevation myocardial infarction is known to be associated with worse short-term outcome than non-ST-segment elevation myocardial infarction. However, whether or not this trend holds true in patients with a high Killip class has been unclear.

Methods

We analyzed 3704 acute myocardial infarction patients with Killip II–IV class from the Japan Acute Myocardial Infarction Registry and compared the short-term outcomes between ST-segment elevation myocardial infarction (n = 2943) and non-ST-segment elevation myocardial infarction (n = 761). In addition, we also performed the same analysis in different age subgroups: <80 years and ≥80 years.

Results

In the overall population, there were no significant difference in the in-hospital mortality (20.0% vs 17.1%, p = 0.065) between ST-segment elevation myocardial infarction and non-ST-segment elevation myocardial infarction groups. Patients <80 years of age also showed no difference in the in-hospital mortality (15.7% vs 15.2%, p = 0.807) between ST-segment elevation myocardial infarction (n = 2001) and non-ST-segment elevation myocardial infarction (n = 453) groups, whereas among those ≥80 years of age, ST-segment elevation myocardial infarction (n = 942) was associated with significantly higher in-hospital mortality (29.3% vs 19.8%, p = 0.001) and in-hospital cardiac mortality (23.3% vs 15.0%, p = 0.002) than non-ST-segment elevation myocardial infarction (n = 308). After adjusting for covariates, ST-segment elevation myocardial infarction was a significant predictor for in-hospital mortality (odds ratio 2.117; 95% confidence interval, 1.204–3.722; p = 0.009) in patients ≥80 years of age.

Conclusion

Among cases of acute myocardial infarction with a high Killip class, there was no marked difference in the short-term outcomes between ST-segment elevation myocardial infarction and non-ST-segment elevation myocardial infarction in younger patients, while ST-segment elevation myocardial infarction showed worse short-term outcomes in elderly patients than non-ST-segment elevation myocardial infarction. Future study identifying the prognostic factors for the specific anticipation intensive cares is needed in this high-risk group.

Introduction

In the past few decades, the rate of in-hospital mortality for acute myocardial infarction (AMI) has markedly declined thanks to the increase of primary percutaneous coronary intervention (PCI) and advances in pharmacotherapy. Nevertheless, AMI with decompensated heart failure or cardiogenic shock at the timing of admission, which has been classically categorized by Killip classification, still carries a higher risk of in-hospital death.^1–5

According to the current guidelines, the clinical spectrum of AMI has been classified based on the presenting electrocardiogram (ECG) into ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation myocardial infarction (NSTEMI). This subdivision has important clinical implications in terms of early risk stratification, as STEMI has a higher risk of short-term mortality than NSTEMI.^6–9 However, whether or not this electrocardiographic classification of AMI has significant implications remains unclear even among the patients presenting with heart failure and/or cardiogenic shock.

The management of elderly AMI patients is also a global topic of interest in this era of aging populations, as several studies have shown worse clinical outcomes in elderly AMI patients than in younger AMI patients,^10–12 despite the increasing number of early primary PCI procedures performed for this older population.^12–14 Furthermore, a nationwide real-world analysis of the Japan Acute Myocardial Infarction Registry (JAMIR) showed feasibility and efficacy of primary PCI for AMI patients aged ≥80 years.¹³

Therefore, in the present sub-analysis of the JAMIR study, we compared in-hospital mortality and in-hospital cardiac death between STEMI and NSTEMI patients complicated with Killip class II–IV. In addition, in order to evaluate the impact of age on this analysis, we performed the same comparison in a younger subgroup (<80 years of age) and in an older subgroup (≥80 years of age).

Methods

The study registry

For this observational retrospective study, we analyzed the data from the JAMIR registry, which is a nationwide multicenter AMI registry including patients who were admitted and diagnosed as spontaneous AMI following the criteria of the Joint European Society of Cardiology/American Heart Association/World Heart Federation Task Force¹⁵ or World Health Organization (WHO) Monitoring of Trends and Determinants in Cardiovascular Disease (MONICA) project¹⁶ within 24 h from onset between January 2011–December 2013. This registry did not include patients with AMI associated with PCI or coronary artery bypass grafting (CABG).

Among the 20,462 patients enrolled in the registry, the study population of the current analysis consisted of 3704 AMI patients with Killip class II–IV, excluding those with patients who showed Killip class I or whose Killip classification was unknown (Figure 1). STEMI was diagnosed when ST elevation ≥1 mm was seen in at least two contiguous leads at any location on the index or qualifying ECG, when new left bundle branch block was presumed, or when new Q waves were observed. In the absence of ST-segment elevation, patients meeting the diagnostic criteria for myocardial infarction (MI) were considered to have NSTEMI. We also excluded patients in whom STEMI or NSTEMI could not to be determined. The major outcomes in the present study were in-hospital all-cause mortality and in-hospital cardiac mortality. The study was conducted in accordance with the tenets of the Declaration of Helsinki. The institutional review boards of all participating centers approved the present study.

Figure 1.

Flow chart of patients in the study analyses. AMI: acute myocardial infarction; JAMIR: Japan Acute Myocardial Infarction Registry; NSTEMI: non-ST-segment elevation myocardial infarction; STEMI: ST-segment elevation myocardial infarction.

Data analyses

We compared the baseline characteristics and in-hospital outcomes between STEMI and NSTEMI in the overall population as well as in patients aged <80 and aged ≥80 years of age. In addition, we also compared the in-hospital outcomes between STEMI and NSTEMI in the Killip class II, III, and IV groups. Characteristics of patients and clinical variables were summarized as means with standard deviations. Categorical variables were expressed as numbers and percentages. Continuous variables were compared using the t-test. Categorical variables were analyzed using the chi-squared test. A logistic univariate regression analysis was performed to evaluate associations between clinical variables and in-hospital mortality or cardiac mortality in patients <80 and ≥80 years of age. In addition, a logistic multivariate regression analysis was performed to evaluate significant predictors for in-hospital outcomes in these groups. Statistical significance was defined as a p-value <0.05. All statistical analyses were performed using the IBM SPSS Statistics software program, ver. 24 (IBM Corporation, Armonk, New York, USA).

Results

Baseline patient characteristics

Table 1 shows the baseline characteristics of the patients in this study. Of the total 3704 AMI patients, 2943 had STEMI, and 761 had NSTEMI (Figure 1). STEMI patients showed a higher rate of smoking, performance of emergency coronary angiography (CAG), PCI, anterior MI, Killip IV class, use of intra-aortic balloon pumping (IABP), and extracorporeal membrane oxygenation (ECMO) than NSTEMI patients. In contrast, NSTEMI patients had an older age and higher rates of hypertension, dyslipidemia, diabetes, and left main trunk (LMT) disease than STEMI patients.

Table 1.

Baseline patient characteristics in the overall population.

	Overall populationn = 3704	STEMI n = 2943	NSTEMI n = 761	p-Value
Age (years)	72.7±12.6	72.2±12.7	74.7±12.2	0.001
Male (%)	69.5	70.2	67.2	0.107
Hypertension (%)	66.2	64.5	72.6	0.001
Dyslipidemia (%)	39.2	39.2	43.5	0.039
Diabetes (%)	37.3	35.5	43.8	0.001
Smoking (%)	28.9	29.7	25.6	0.038
Emergency CAG (%)	85.9	88.5	76.4	0.001
PCI (%)	84.2	86.8	73.3	0.001
Anterior MI (%)	56.1	57.8	48.4	0.001
LMT disease (%)	8.1	7.0	12.7	0.001
Killip IV (%)	33.4	34.9	27.5	0.001
IABP (%)	32.4	33.8	26.9	0.001
ECMO (%)	6.5	7.1	4.1	0.006

CAG: coronary angiography; ECMO: extracorporeal membrane oxygenation; IABP: intra-aortic balloon pumping; LMT: left main trunk; MI: myocardial infarction; NSTEMI: non-ST-segment elevation myocardial infarction; PCI: percutaneous coronary intervention; STEMI: ST-segment elevation myocardial infarction.

Data are expressed as the mean±standard deviation or percentage.

^aComparison between STEMI and NSTEMI.

As shown in Table 2, we analyzed the patients in two age groups, <80 years of age (n = 2454) and ≥80 years of age (n = 1250). The subgroup of patients <80 years of age included 2001 STEMI and 453 NSTEMI patients. In this subgroup, the STEMI patients showed higher rates of performance of emergency CAG, PCI, anterior MI, and use of IABP than the NSTEMI patients. In contrast, the NSTEMI patients showed an older age and higher rates of hypertension, dyslipidemia, diabetes, and LMT disease than the STEMI patients. The subgroup of patients ≥80 years of age included 942 STEMI and 308 NSTEMI patients. In this subgroup, the STEMI patients showed higher rates of emergency CAG, PCI, and Killip IV class than the NSTEMI patients. In contrast, the prevalence of LMT disease was higher in the NSTEMI patients than in the STEMI patients.

Table 2.

Baseline patient characteristics by age subgroups.

	<80 years old n = 2454			≥80 years old n = 1250
	STEMI n = 2001	NSTEMI n = 453	p-Value	STEMI n = 942	NSTEMI n = 308	p-Value
Age (years)	65.9±10.0	67.1±9.7	0.016	85.8±4.5	85.9±4.2	0.684
Male (%)	80.3	77.3	0.145	48.6	52.3	0.266
Hypertension (%)	61.8	70.3	0.001	70.1	75.8	0.068
Dyslipidemia (%)	43.5	50.0	0.019	30.1	34.3	0.192
Diabetes (%)	38.0	52.1	0.001	30.2	31.8	0.624
Smoking (%)	38.3	34.8	0.191	11.5	12.3	0.745
Emergency CAG (%)	92.7	83.8	0.001	79.6	65.6	0.001
PCI (%)	89.8	76.2	0.001	80.0	68.4	0.001
Anterior MI (%)	59.5	48.0	0.001	53.6	49.3	0.271
LMT disease (%)	7.7	14.4	0.001	5.4	9.7	0.034
Killip IV (%)	35.9	31.8	0.092	32.7	21.1	0.001
IABP (%)	38.1	31.4	0.015	24.8	20.3	0.137
ECMO (%)	9.2	6.2	0.055	2.6	1.1	0.151

CAG: coronary angiography; ECMO: extracorporeal membrane oxygenation; IABP: intra-aortic balloon pumping; LMT: left main trunk; MI: myocardial infarction; NSTEMI: non-ST-segment elevation myocardial infarction; PCI: percutaneous coronary intervention; STEMI: ST-segment elevation myocardial infarction.

Data are expressed as the mean±standard deviation or percentage.

In-hospital outcomes

As seen in Figure 2, in-hospital mortality and cardiac mortality showed a gradual increase as the Killip class became higher. This analysis also showed no significant differences in the in-hospital mortality or cardiac mortality between STEMI and NSTEMI in any of the assessed Killip groups.

Figure 2.

In-hospital outcomes in ST-segment elevation myocardial infarction (STEMI) and non-STEMI (NSTEMI) among different Killip classes.

Figure 3 shows a comparison of the in-hospital outcomes between STEMI and NSTEMI in the overall population and patients <80 and ≥80 years of age. In the overall population, there were no significant differences in the in-hospital mortality (STEMI 20.0% vs NSTEMI 17.1%, p = 0.065) and in-hospital cardiac mortality (STEMI 15.5% vs NSTEMI 13.8%, p = 0.256) between STEMI and NSTEMI. In the patients aged <80 years of age, there was also no difference in the in-hospital mortality (STEMI 15.7% vs NSTEMI 15.2%, p = 0.807) or in-hospital cardiac mortality (STEMI 11.9% vs NSTEMI 13.0%, p = 0.495) between STEMI and NSTEMI. However, in the patients aged ≥80 years of age, STEMI showed a higher level of in-hospital mortality (STEMI; 29.3% vs NSTEMI; 19.8%, p = 0.001) and in-hospital cardiac mortality (STEMI; 23.3% vs NSTEMI 15.0%, p = 0.002) than NSTEMI.

Figure 3.

In-hospital outcomes in ST-segment elevation myocardial infarction (STEMI) and non-STEMI (NSTEMI) among different age groups.

Table 3 shows a logistic regression analysis for the in-hospital outcomes in patients <80 years of age. The univariate analysis in this younger subgroup showed that STEMI was not associated with in-hospital mortality and in-hospital cardiac mortality. Multivariate analysis in this subgroup showed that age, anterior MI, PCI, Killip IV class, IABP, and ECMO were significant predictors for in-hospital mortality, while PCI, Killip IV class, IABP, and ECMO were significant predictors for in-hospital cardiac mortality.

Table 3.

Results of logistic regression analyses for the in-hospital outcomes in patients <80 years of age.

	<80 years old (n = 2454)
	In-hospital mortality				In-hospital cardiac mortality
Variables	Univariate analysis OR (95% CI)	p-Value	Multivariate analysis OR (95% CI)	p-Value	Univariate analysis OR (95% CI)	p-Value	Multivariate analysis OR (95% CI)	p-Value
Age (years)	1.017 (1.006–1.029)	0.003	1.021 (1.003–1.039)	0.023	1.017 (1.003–1.030)	0.017	1.013 (0.992–1.034)	0.215
Male	0.955 (0.730–1.249)	0.736	1.011 (0.670–1.527)	0.957	0.872 (0.650–1.169)	0.359	0.864 (0.544–1.371)	0.534
Hypertension	0.760 (0.594–0.972)	0.029	0.959 (0.679–1.355)	0.813	0.723 (0.548–0.954)	0.022	0.877 (0.594–1.295)	0.509
Dyslipidemia	0.688 (0.536–0.884)	0.003	0.945 (0.670–1.332)	0.745	0.608 (0.456–0.812)	0.001	0.760 (0.508–1.135)	0.180
Diabetes	0.965 (0.755–1.235)	0.780	–	–	0.868 (0.656–1.149)	0.322	–	–
Smoking	0.784 (0.605–1.015)	0.065	–	–	0.722 (0.536–0.972)	0.032	0.770 (0.505–1.173)	0.223
Anterior MI	1.469 (1.150–1.876)	0.002	1.476 (1.035–2.104)	0.031	1.524 (1.155–2.011)	0.003	1.361 (0.906–2.046)	0.138
LMT disease	2.540 (1.780–3.623)	0.001	0.734 (0.422–1.276)	0.273	2.868 (1.960–4.195)	0.001	0.881(0.486–1.599)	0.678
PCI	0.500 (0.373–0.671)	0.001	0.555 (0.341–0.902)	0.017	0.516 (0.373–0.714)	0.001	0.531 (0.300–0.876)	0.015
Killip IV	7.031 (5.498–8.992)	0.001	4.246 (3.014–5.981)	0.001	6.955 (5.269–9.182)	0.001	3.509 (2.353–5.234)	0.001
IABP	3.542 (2.761–4.544)	0.001	1.825 (1.279–2.603)	0.001	3.633 (2.739–4.819)	0.011	1.853 (1.217–2.821)	0.004
ECMO	13.145 (9.402–18.380)	0.001	9.198 (6.014–14.069)	0.001	12.460 (8.874–17.496)	0.001	8.214 (5.277–12.786)	0.001
STEMI (vs NSTEMI)	1.036 (0.780–1.375)	0.807	0.833 (0.539–1.288)	0.412	0.899 (0.663–1.220)	0.495	0.736 (0.450–1.204)	0.222

CI: confidence interval; ECMO: extracorporeal membrane oxygenation; IABP: intra-aortic balloon pumping; LMT: left main trunk; MI: myocardial infarction; NSTEMI: non-ST-elevation myocardial infarction; OR: odds ratio; PCI: percutaneous coronary intervention; STEMI: ST-segment elevation myocardial infarction.

Table 4 shows a logistic regression analysis for the in-hospital outcomes in patients ≥80 years of age. In this older subgroup, the univariate analysis showed that STEMI was a significant determinant for in-hospital mortality (odds ratio (OR) 1.678; 95% confidence interval (CI), 1.227–2.296; p = 0.001) and in-hospital cardiac mortality (OR 1.707, 1.205–2.417; p = 0.003). Even after adjustment for covariates in the multivariate analysis, STEMI remained independently of prognostic significance for in-hospital mortality (OR 2.117, 1.204–3.722, p = 0.009). On the other hand, in multivariate analysis for in-hospital cardiac mortality, STEMI was not a statistically significant predictor (OR 1.765, 0.947–3.289, p = 0.074).

Table 4.

Results of logistic regression analyses for the in-hospital outcomes in patients ≥80 years of age.

	≥80 years old (n = 1250)
	In-hospital mortality				In-hospital cardiac mortality
Variables	Univariate analysis OR (95% CI)	p-Value	Multivariate analysis OR (95% CI)	p-Value	Univariate analysis OR (95% CI)	p-Value	Multivariate analysis OR (95% CI)	p-Value
Age (years)	1.100 (1.070–1.132)	0.001	1.116 (1.063–1.173)	0.001	1.122 (1.089–1.157)	0.001	1.142 (1.082–1.205)	0.001
Male	0.851 (0.663–1.094)	0.208	1.180 (0.796–1.751)	0.410	0.699 (0.531–0.919)	0.010	1.041 (0.672–1.613)	0.857
Hypertension	0.985 (0.733–1.324)	0.920	–	–	1.130 (0.813–1.571)	0.467	–	–
Dyslipidemia	0.592 (0.435–0.806)	0.001	0.530 (0.333–0.844)	0.007	0.627 (0.447–0.881)	0.007	0.590 (0.350–0.994)	0.048
Diabetes	0.954 (0.713–1.278)	0.754	–	–	0.797 (0.574–1.108)	0.177	–	–
Smoking	0.715 (0.454–1.128)	0.149	–	–	0.688 (0.412–1.149)	0.153	–	–
Anterior MI	1.625 (1.200–2.200)	0.002	1.642 (1.097–2.459)	0.016	1.686 (1.203–2.365)	0.002	1.544 (0.987–2.418)	0.057
LMT disease	2.071 (0.167–3.678)	0.013	1.095 (0.504–2.380)	0.819	2.133 (0.157–3.930)	0.015	1.279 (0.566–2.889)	0.554
PCI	0.384 (0.285–0.518)	0.001	0.507 (0.286–0.901)	0.021	0.357 (0.260–0.491)	0.001	0.472 (0.255–0.873)	0.017
Killip IV	3.973 (3.046–5.182)	0.001	3.143 (2.072–4.768)	0.001	4.053 (3.050–5.385)	0.001	3.509 (2.215–5.559)	0.001
IABP	1.775 (1.309–2.403)	0.001	2.719 (1.749–4.228)	0.001	1.536 (1.105–2.137)	0.011	2.436 (1.490–3.983)	0.001
ECMO	7.004 (2.873–17.074)	0.001	3.219 (1.086–9.548)	0.035	4.676 (2.065–10.588)	0.001	1.997 (0.704–5.669)	0.194
STEMI (vs NSTEMI)	1.678 (1.227–2.296)	0.001	2.117 (1.204–3.722)	0.009	1.707 (1.205–2.417)	0.003	1.765 (0.947–3.289)	0.074

CI: confidence interval; ECMO: extracorporeal membrane oxygenation; IABP: intra-aortic balloon pumping; LMT: left main trunk; MI: myocardial infarction; NSTEMI: non-ST-elevation myocardial infarction; OR: odds ratio; PCI: percutaneous coronary intervention; STEMI: ST-segment elevation myocardial infarction.

Discussion

The main findings of this study were (a) in AMI patients with Killip classes II–IV classes, there were no significant differences in the in-hospital mortality or in-hospital cardiac mortality between STEMI and NSTEMI patients, (b) and the same result was found in the subgroup <80 years of age; however, (c) in patients aged ≥80 years of age, STEMI showed a significantly higher in-hospital mortality than NSTEMI.

This study compared the in-hospital outcomes between patients with STEMI and NSTEMI presenting with heart failure or cardiogenic shock, which is recognized as a high-risk population. According to their baseline characteristics, the patients in the present study were older (72.7 vs 68.8 years old) than those in the previous JAMIR registry analysis of overall patients,¹³ but similar to those in a previous registry that investigated AMI with heart failure in Europe (73 years old)¹⁷ and USA (74 years old).¹⁸ In-hospital mortalities of our study were 20.0% in STEMI and 17.1% in NSTEMI, which were also similar with that found in a large-scale US registry of patients with AMI complicating congestive heart failure.¹⁹

The Killip classification for the severity of heart failure has proven useful for the early risk stratification of AMI patients.^1,2,20 On the other hand, heart failure on hospital admission is associated with an approximately three- to four-fold increase in hospital death rates even in the primary PCI era.^17,18 Thus, our investigation focused on this high-risk population. Previous studies have shown that STEMI has a worse short-term prognosis than NSTEMI,^6–9,21,22 whereas NSTEMI was associated with a higher long-term mortality risk than STEMI.^7,9,23 On the other hand, our analysis for the overall population or younger patients <80 years of age found that STEMI and NSTEMI with high Killip class had comparable in-hospital outcomes. These findings indicate that ECG-based classification of AMI may have relatively little prognostic value for index hospitalization, especially in younger AMI patients with high Killip class.

From the perspective of pathophysiology, AMI-triggered acute heart failure (AHF) exacerbates coronary ischemia and decrease of myocardial contraction, leading to further increase of left ventricular filling pressure and pulmonary edema.²⁴ Furthermore, the activated sympathetic nerve system and renin-angiotensin-system due to coronary ischemia may also accelerate this vicious cycle, leading to an incidence of fatal cardiovascular events. Previous reports showed that AHF with acute coronary syndrome (ACS) had worse short-term prognosis but equivalent long-term prognosis compared to AHF without ACS,^25,26 suggesting that coronary ischemia and congestive heart failure could synergically increase the short-term cardiovascular events. Under the condition of AMI-triggered AHF, therefore, whether infarction is transmural or non-transmural may not be major issue at least in terms of in-hospital prognosis.

Our findings also indicate that NSTEMI with a high Killip class should be treated as intensively as STEMI just after admission. A recent study reported that immediate PCI strategy was superior to conservative strategy even in patients ≥80 years of age with non-ST-segment elevation ACS,²⁷ suggesting that early invasive treatment might be beneficial for high-risk NSTEMI patients. In general, the short-term outcome of NSTEMI is better than that of STEMI because of the smaller infarction size.^6–8,21,22 However, NSTEMI includes a heterogeneous risk group of patients in terms of the territory of the infarction area and underlying severity of coronary artery disease (CAD). For example, single-vessel occlusion of the left circumflex artery often presents as relatively low-risk NSTEMI,²⁸ whereas LMT or three-vessel disease also presents with non-ST elevation type ECG changes.^29,30 Therefore, our study might have included more high-risk NSTEMI patients with advanced CAD than typical cohorts, which could be one of the explanations for the high mortality of NSTEMI.

In the patients ≥80 years of age, however, STEMI showed worse in-hospital outcomes than NSTEMI, despite PCI being performed more frequently in STEMI than NSTEMI.

These results indicated that the detection of ST-elevation still remains significant with regard to clinical implications in elderly patients, even in the cases with a high Killip class. In our multivariate analysis, interestingly, STEMI was a significant determinant of the in-hospital mortality even after adjusting for Killip IV class, suggesting that a high rate of cardiogenic shock in elderly STEMI patients was not enough explanation for their worse in-hospital mortality than NSTEMI. In general, the fatal cardiac arrhythmias and mechanical complications such as cardiac rupture, ventricular septal perforation, and papillary muscle rupture, can cause a catastrophic condition during the early phase of STEMI,^31,32 especially in older patients with a high Killip class.³³ Thus, these complications could be explanations of the high rate of in-hospital death of elderly patients of our study. Recent studies have reported the possibility that total hospital stay and coronary care unit (CCU) stay for AMI patients could be shortened in the cases with low or intermediate risk.^34,35 However, our present findings suggest that elderly STEMI patients with high Killip class may need a longer CCU stay than NSTEMI or younger patients, even after successful primary PCI. Furthermore, these high-risk patients require careful observation for life-threatening arrhythmia or mechanical complications even in the post-CCU phase. Future studies should investigate the optimal in-hospital management for elderly STEMI patients with a high Killip class. In addition, further studies with more focus on pathophysiology and specific treatment for AMI-triggered AHF will be needed.

Limitations

Our study has several limitations. First, as the present study was a nonrandomized and retrospective observational study, residual confounding or selection bias cannot be completely excluded as an alternative explanation of our findings. Second, we did not show the data of peak creatinine kinase, left ventricular ejection fraction, and brain natriuretic peptide, which are known as independent predictors of AMI or heart failure patients. Thus, we were unable to adjust for these factors in the present analysis. Third, we collected no data on the complexity of the diseased vessels, such as the presence of multivessel disease or the “Synergy between PCI with Taxus and Cardiac Surgery” (SYNTAX) score, which may influence the prognosis, especially in NSTEMI patients with high Killip class. Fourth, lack of detailed data of PCI procedure, including stent types (bare metal stent or drug-eluting stent), number of revascularized vessels, and reperfusion time represents a major constraint on this study.

Conclusion

In AMI cases with a moderate to high Killip class, there was no significant difference in the in-hospital mortality or cardiac death rates between STEMI and NSTEMI among patients <80 years of age; however, elderly STEMI patients ≥80 years of age showed worse in-hospital mortality than elderly NSTEMI patients. Future studies identifying the prognostic factors for the specific anticipation of intensive care and optimal treatment strategies are needed in this high-risk elderly group.

 

Appendix

JAMIR Investigators

Sapporo ACS Network: Takashi Takenaka (Hokkaido Medical Center), Daisuke Hotta (Hokkaido Cardiovascular Hospital); Iwate ACS Registry: Tomonori Itoh (Iwate Medical University School of Medicine); Yamagata AMI Registry: Tetsu Watanabe (Yamagata University School of Medicine); Miyagi AMI Registry Study: Kiyotaka Hao (Tohoku University); Jichi Medical University: Kazuomi Kario; Tokyo CCU Network: Takeshi Yamamoto (Nippon Medical School Hospital); Naoki Sato (Nippon Medical School Musashi-Kosugi Hospital); Atsuo Namiki (Kanto Rosai Hospital); Hiroshi Suzuki (Showa University Fujigaoka Hospital); Makoto Suzuki (Sakakibara Heart Institute); Yokohama Cardiovascular Workshop: Masami Kosuge (Yokohama City University Medical Center); Mie ACS Registry Masaaki Ito (Mie University); Takashi Tanigawa (Matsusaka Chuo Hospital); NCVC AMI Registry: Yasuhide Asaumi (National Cerebral and Cardiovascular Center); Kumamoto Acute Coronary Events Study: Kenichi Tsujita (Kumamoto University); JAMIR data center: Yoshihiro Miyamaoto (National Cerebral and Cardiovascular Center).

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported in part by a Grant-in-Aid for Scientific Research (17K09542) from the Ministry of Education, Science, and Culture, Japan.

Conflict of interest: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.