Early ventricular tachycardia (VT) and ventricular fibrillation (VF) are associated with increased in-hospital mortality but do not influence the long-term prognosis in ST-elevation myocardial infarction (STEMI). Recent data advocate a differential approach to the type of arrhythmia and indicate long-term mortality hazard associated with monomorphic VT. We aimed to evaluate the prognostic value of early monomorphic VT compared to nonmonomorphic VT/VF in a nonselected cohort of STEMI patients. Consecutive STEMI patients admitted for primary percutaneous coronary intervention from 2007 to 2010 were included. Clinical characteristics were obtained from the Swedish national SWEDEHEART registry. The occurrence and type of early VT/VF were verified in medical records. All-cause mortality 8 years after STEMI was assessed using the Swedish Cause of Death Register. A total of 2,277 STEMI patients were included (age 66 ± 12 years, 70% male), among them 35 (1.5%) with early monomorphic VT and 115 (5.1%) with nonmonomorphic VT/VF. Patients with monomorphic VT had similar clinical characteristics compared to those with nonmonomorphic VT/VF. In total, 22 patients (63%) with monomorphic VT and 43 (37%) with nonmonomorphic VT/VF died by 8 years of follow-up (p = 0.011). Monomorphic VT was associated with a higher risk of all-cause mortality compared to nonmonomorphic VT/VF in univariate analysis (HR 2.03, 95% CI 1.21 to 3.39, p = 0.007) and after adjustment for age and history of myocardial infarction (MI) (HR 1.74, 95% CI 1.02 to 2.97, p = 0.041). Early monomorphic VT in STEMI is associated with a higher risk of all-cause mortality compared to nonmonomorphic VT/VF and deserves further studies to refine risk stratification strategies.
Malignant ventricular arrhythmias occurring early during ST-elevation myocardial infarction (STEMI) are known to markedly contribute to increased in-hospital mortality, but not to influence the long-term prognosis. , Most of the clinical studies that focused on ventricular arrhythmias during STEMI, analyzed ventricular tachycardia (VT) and ventricular fibrillation (VF) together. During the last decade, a possible link between the monomorphic VT and increased mortality was reported in patients with the acute coronary syndrome who were revascularized. , However, these studies included patients with both STEMI, non-STEMI , and even unstable angina, whereas studies on the prognostic significance of different types of ventricular arrhythmias in a homogeneous population of STEMI patients treated with aggressive revascularization protocols are lacking. In this study we aimed to evaluate the prognostic value of monomorphic VT compared to nonmonomorphic VT or VF during the first 48 hours of STEMI in a nonselected cohort of STEMI patients admitted for primary percutaneous coronary intervention (PCI).
Methods
Consecutive STEMI patients admitted to a Lund University hospital for primary PCI from 2007 to 2010 were included. The Swedish national SWEDEHEART registry was used for the assessment of clinical characteristics and the presence of VT/VF during the index admission. The occurrence and the type of ventricular arrhythmia during the first 48 hours from symptom onset (early arrhythmias) , were verified in medical records. Only hemodynamically unstable VT or VF were accounted for. Monomorphic VT was defined as a wide complex tachycardia of ventricular origin at a rate >100 beats per minute with uniform and stable morphology. The group of nonmonomorphic VT included polymorphic VT, which was defined as VT with changing QRS morphology, and VF defined as irregular undulations of varying contour and amplitude on the electrocardiogram with absent distinct QRS and T waves and prompt hemodynamic compromise requiring cardioversion.
After hospital discharge, the patients were followed up to December 31, 2018. Information on implantable cardioverter-defibrillators (ICDs) for primary or secondary prevention was obtained from the hospital register. Medical records were reviewed for the occurrence and adequacy of ICD therapy. ICD shocks and/or antitachycardia pacing for ventricular arrhythmias were defined as adequate ICD therapy.
Information on all-cause mortality and the cause of death, including sudden cardiac death, was obtained from the Swedish Cause of Death Register. The primary end point of this study was total mortality by 8 years of follow-up. The secondary combined end point is composed of recurrent sustained VT/VF, adequate ICD therapy, or sudden cardiac death.
The study was approved by the Regional Ethics Committee in Lund (No. 2010/585, 2010/11/29).
Continuous variables are presented as mean ± SD or median (interquartile range) as appropriate depending on the distribution. Variables were compared across groups using chi-square or Fisher’s exact test for categorical variables and Student t test for continuous variables with an approximate normal distribution, or Mann-Whitney U test, as appropriate. P values <0.05 were considered significant. The association between the presence and the type of arrhythmia during STEMI and total mortality was tested using Cox regression. All analyses were performed using IBM SPSS Statistics for Windows, version 26.0 (IBM Corp., Armonk, New York).
Results
During the period from 2007 to 2010, 2,277 consecutive STEMI patients were admitted for primary PCI. A total of 23 patients with incomplete medical records were excluded, and 2,254 patients constituted the study group. Early monomorphic VT during index STEMI was documented in 35 patients (1.5%) and nonmonomorphic VT or VF in 115 patients (5.1%). In those with monomorphic VT, in 15 (42.9%) arrhythmias occurred before reperfusion, in 10 (22.6%) accompanied reperfusion, in 3 (8.6%) manifested after reperfusion during the first day of STEMI, in 7 (20%) during the second day of STEMI. Most episodes of nonmonomorphic VT/VF occurred before reperfusion; no nonmonomorphic VT/VF was observed during the second day of STEMI ( Figure 1 ) Twelve.
Patients with monomorphic VT had similar clinical characteristics compared to those with nonmonomorphic VT/VF with a trend of higher prevalence of history of MI by index admission among those with monomorphic VT ( Table 1 ). The angiography revealed a higher proportion of left main stenosis in patients with monomorphic VT; the infarct-related artery distribution and the proportion of multivessel disease did not differ between groups. Primary PCI was not performed in 171 patients due to technical problems or uncertain culprit lesions; in 73 of these patients, coronary artery bypass graft surgery was done.
| Characteristic | No VF (n = 2,104) | Monomorphic VT (n = 35) | Polymorphic VT/ VF (n = 115) |
|---|---|---|---|
| Age (years) | 66.4 ± 12.0 | 68.5 ± 11.6 | 66.4 ± 11.6 |
| Men | 1,465 (69.6%) | 27 (77%) | 83 (72%) |
| Diabetes mellitus | 270 (12.9%) | 3 (9%) | 9 (8%) |
| Hypertension | 849 (40.5%) | 10 (29%) | 54 (48%) |
| Prior myocardial infarction | 290 (13.8%) | 11 (31%) | 24 (21%) |
| Prior CABG | 75 (3.6%) | 3 (9%) | 7 (6%) |
| Prior PCI | 202 (9.6%) | 4 (12%) | 15 (13%) |
| Prior stroke | 138 (6.6%) | 3 (9%) | 8 (7%) |
| Chronic heart failure | 67 (3.2%) | 2 (6%) | 5 (4.3%) |
| Anterior myocardial infarction | 874 (44.9%) | 19 (58%) | 51 (45%) |
| Killip class IV at admission | 41 (2%) | 4 (11%) | 11(10%) |
| Potassium level at admission (mmol/L) | 3.9 ± 0.4 | 3.9 ± 0.5 | 3.8 ± 0.5 |
| Creatinine level at admission (mmol/L) | 80 (29) | 85 (39) | 87 (49) |
| Symptom-PCI time (minutes) | 217 (245) | 199 (150) | 179 (192) |
| Multivessel coronary disease | 1,024 (55.4%) | 22 (69%) | 66 (62%) |
| Infarct-related coronary artery: | |||
| Left anterior descending | 803 (42.7%) | 16 (50%) | 44 (40%) |
| Right coronary artery | 737 (39.1%) | 11 (34%) | 44 (40%) |
| Left main stenosis | 99 (5.3%) | 9 (28%) | 12 (11%) |
| Characteristic of stenosis: | |||
| Occlusion in IRA <3 months | 1,349 (75.3%) | 26 (79%) | 88 (83%) |
| Chronic occlusion | 26 (1.5%) | 2 (6%) | 3 (3%) |
| Non-occlusive stenosis in IRA | 416 (23.2%) | 5 (15%) | 15 (14%) |
| PCI performed | 1,936 (92.1%) | 33 (94%) | 112 (97%) |
| CABG performed | 70 (3.3%) | 2 (6%) | 1 (1%) |
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