Methods

This prospective register of patients with MI was undertaken by 6 public hospitals in Spain, with long-term follow-up of vital status. All patients aged >18 years who were admitted with first MI <72 hours after symptom onset were prospectively and consecutively included from September 2001 to June 2003. The study was approved by the local ethics committee, and all participants were informed and provided signed consent.

The diagnosis of MI followed the European Society of Cardiology and American College of Cardiology definition, which is that MI is a myocardial necrosis secondary to ischemia. Myocardial necrosis is defined as elevated levels of troponin T or I, or of the creatine kinase-MB fraction, according to the normal levels as defined at each center.

On the basis of electrocardiographic findings at admission, patients were classified into 3 groups: STEMI, NSTEMI or unclassified MI (presence of left branch block or pacemaker rhythm). All electrocardiograms were analyzed by a clinical cardiologist at each of the participant hospitals using standardized criteria.

Exclusion criteria were a history of MI, residence outside the center’s service area, and serious illness, unrelated to the admission episode, that limited the patient’s life expectancy.

A standardized questionnaire administered by trained personnel was used to prospectively gather demographic variables and co-morbidities such as history of hypertension, diabetes, hypercholesterolemia, smoking, and previous angina. Clinical characteristics of the event were recorded, including MI location, presence of ST-segment elevation on admission electrocardiography, appearance of Q waves, and complications such as the development of pulmonary edema or cardiogenic shock or the presence of malignant arrhythmias within the first 48 hours (defined as the appearance of ventricular fibrillation or sustained ventricular tachycardia requiring immediate medical attention). Finally, information was also collected on the management of the acute event, including medical treatments during the hospital stay and at discharge, reperfusion and procedures such as pharmacologic or stress-testing techniques to determine the presence of ischemia, echocardiography, coronary angiography (number of vessels with severe lesions), and surgical or percutaneous coronary revascularization.

No standards were established for clinical management of the patients, so each of the participating hospitals used its own treatment protocols. Nonetheless, all the hospitals used protocols that followed the national and international clinical practice guidelines in force at the time of the study.

Events of interest were defined as 28-day and long-term mortality, with 7-year follow-up of vital status until December 31, 2009. To identify long-term fatal cases, we accessed the National Death Registry. This is an exhaustive and mandatory official database collecting individual data of all individuals who have died in Spain from 1987 until the present. This database is promoted by the Spanish health ministry to public institutions (health care administrations, research centers, etc) and provides information regarding vital status and date of death, although it does not indicate a specific cause of death. We used individual data of the patients included in this registry (family name, name, date of birth, city of residence) to link our data with the National Death Registry. Given the demographic trends of the study area, specifically the lack of international out-migration, we assumed that study participants who did not appear in this registry were alive at the end of the follow-up.

In the comparison of the 3 study groups (STEMI, NSTEMI, and unclassified MI), analysis of variance or the Kruskal-Wallis test was used for continuous variables and the chi-square test for categorical variables. Logistical regression and Cox regression were used to determine the associations between the 3 electrocardiographic patterns and 28-day and long-term mortality, respectively, adjusting for the confounding variables identified. We tested for the interaction between the use of revascularization procedures during hospitalization and the 3 electrocardiographic patterns on 28-day and 7-year prognoses.

In the multivariate analyses, multiple imputation methods were performed to replace missing values in the adjustment variables, for which the “mi” and “mitools” R packages were used, and to avoid potential selection bias and loss of statistical power. A p value <0.05 was considered significant. R version 2.11.1 (R Foundation for Statistical Computing, Vienna, Austria) was used for the analysis.

Results

The study registered consecutively 3,842 patients. After excluding those patients with exclusion criteria ( Figure 1 ) , 2,048 were included in the analyses: 60.3% with STEMI, 32.7% with NSTEMI, and 7.0% with unclassified MI. The demographic and clinical characteristics of the 3 patient groups are listed in Table 1 . Patients with NSTEMI had a higher prevalence of cardiovascular risk factors (hypertension, tobacco use, and diabetes) and previous angina and a larger proportion of women than in the STEMI group. Patients with unclassified MI were older and also had a higher prevalence of cardiovascular risk factors and angina than the STEMI group.

Flowchart of registered and included patients in the study.

The variables associated with the electrocardiographic typology of MI in multivariate analysis are listed in Table 2 . History of angina, arterial hypertension, and age were associated with a higher probability of NSTEMI than of STEMI. In addition, age was directly associated with a higher probability of presenting with unclassified MI than with NSTEMI.

In contrast, analysis of the patients who received coronary angiography showed that patients with NSTEMI presented with a higher proportion of multivessel disease.

The treatments and procedures implemented during the hospital stay are listed in Table 3 . Nearly 70% of the patients had coronary angiography, and 1/3 of these had percutaneous coronary intervention (PCI). Reperfusion therapies (thrombolysis or primary PCI) were primarily used in STEMI patients, and elective PCI and surgical revascularization were more frequent in the NSTEMI group.

With respect to medical treatments, there were no differences between the groups in the proportion of patients treated with antiaggregants or β blockers, although NSTEMI patients received more glycoprotein IIb/IIIa inhibitors and statins, and angiotensin-converting enzyme inhibitors were less prescribed.

The in-hospital evolution of all 3 groups is listed in Table 3 . Patients with NSTEMI presented a greater frequency of post-MI angina than those with STEMI but a lower frequency of ventricular arrhythmias and complete atrioventricular block. The 28-day case fatality was higher in STEMI than in NSTEMI patients, although the highest case fatality was observed in those with unclassified MI.

Multivariate analysis showed that patients with STEMI had a higher probability of 28-day case fatality than the NSTEMI group ( Table 4 ). In contrast, patients with unclassified MI had worse 28-day case fatality than patients with STEMI, and this higher mortality was mainly related to a higher proportion of complications, such as Killip class III or IV or ventricular arrhythmias ( Table 4 ).

Table 4

Association between electrocardiographic pattern on admission and 28-day case fatality, adjusted by various covariates in logistic regression models

		STEMI		Unclassified MI
	NSTEMI	OR (95% CI)	p Value	OR (95% CI)	p Value
All patients	n = 670	n = 1,235		n = 143
Model 1	1	1.83 (1.10–3.06)	0.020	4.25 (2.16–8.34)	<0.001
Model 2	1	2.07 (1.23–3.50)	0.007	4.30 (2.16–8.55)	<0.001
Model 3	1	1.85 (1.06–3.25)	0.031	2.43 (1.13–5.22)	0.023
Model 4	1	2.09 (1.17–3.74)	0.013	2.27 (1.02–5.07)	0.045
Patients who underwent revascularization	n = 333	n = 573		n = 50
Model 1	1	2.07 (0.83–5.14)	0.116	0.96 (0.11–8.08)	0.969
Model 2	1	2.04 (0.80–5.23)	0.136	1.09 (0.13–9.30)	0.938
Model 3	1	1.70 (0.62–4.66)	0.298	0.88 (0.09–8.24)	0.910
Model 4	1	1.83 (0.61–5.49)	0.281	1.64 (0.15–17.40)	0.683
Patients without revascularization	n = 323	n = 612		n = 78
Model 1	1	2.32 (1.15–4.70)	0.019	4.96 (2.01–12.20)	0.001
Model 2	1	2.81 (1.37–5.78)	0.005	4.86 (1.93–12.20)	0.001
Model 3	1	3.05 (1.36–6.82)	0.007	2.54 (0.91–7.10)	0.077
Model 4	1	3.45 (1.51–7.88)	0.003	2.46 (0.85–7.10)	0.096

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. Learning Curve in Transradial Coronary Angiography
2. Change in High-Density Lipoprotein Cholesterol and Risk of Subsequent Hospitalization for Coronary Artery Disease or Stroke Among Patients With Type 2 Diabetes Mellitus
3. Meta-Analysis of Monotherapy Versus Combination Therapy for Pulmonary Arterial Hypertension
4. Clinical Significance of a Single Coronary Artery Arising from the Right Sinus of Valsalva With the Left Anterior Descending Anterior to the Pulmonary Artery and a Retro-Aortic Left Circumflex

Stay updated, free articles. Join our Telegram channel

Join