Epidemiological Features of Non-Sustained Ventricular Tachycardia in Acute Coronary Syndrome with ST Segment Elevation.

: Background: Non-Sustained Ventricular Tachycardia is the most frequent ventricular arrhythmias in acute coronary syndrome with ST segment elevation, the assessment of its incidence and prognosis have been the subject of several international studies, but its epidemiological data is lacking in Algeria. Aims: The main objective of our study is the determination of the frequency of Non-Sustained ventricular tachycardia in acute coronary syndrome with ST segment elevation, the secondary objective was the analysis of predictive factors of this arrhythmia, and related mortality. Methods and materials: In this prospective study, conducted in the cardiology department of Hussein Dey hospital (Algiers-Algeria), 467 patients with acute coronary syndrome with elevated ST segment (87 women and 380 men) were enrolled between 28 February 2014 and 16 July 2015. The average age is 60 ± 13 years; at admission, a Holter recorder was attached for continuous ECG monitoring during 48 hours Kruskal’s ANNOVA or H tests were used for comparison of quantitative variables, χ2 test or Fisher’s exact test, were used for qualitative variables, all tests were performed with 1 st species risk of 5%. Results: The frequency of Non-Sustained Ventricular Tachycardia is 28.3 % (132 patients), CI 95%: [24.2%-32.4%], multivariate analysis identified the following independent predictors: Age ≤ 58 years, current active smoking, presence of akinetic segment in echocardiography, and short time from symptom onset to emergency room. The risk of in-hospital mortality is low, but not significant (Hazard Ration of 0.156. CI 95%: [0.21-1.177], p = 0.072) Conclusion : NonSustained Ventricular tachycardia is the most frequent arrhythmias during acute coronary syndrome with elevated ST segment, its predictive factors according to our study are: Age ≤ 58 years, current active smoking, presence of akinetic segment in echocardiography, and short time from symptom onset to emergency room. The risk of in-hospital mortality is low, but not significant.


Introduction:
Nonsustained ventricular tachycardia (NSVT) defined as ventricular tachycardia lasting less than 30 seconds; is one of the most frequent ventricular arrhythmias, its prognostic implication is controversial, and the results of some international studies are divergent.Repetitive Non-Sustained Ventricular tachycardia may induce hemodynamic instability, and promotes the onset of cardiogenic shock during hospitalization.Its mechanisms are complex and multifactorial; several electrophysiological modifications occur just after coronary artery occlusion, and lead to reentry phenomena, abnormal automatism, and triggered activity.The main objective of our study is to determine the frequency of nonsustained ventricular tachycardia in acute coronary syndrome with ST segment elevation, during the first 48 hours of hospitalization, while the secondary objective is the analysis of its predictive factors and the related mortality.

Methods and materials:
We prospectively studied a group of 467 consecutive patients (380 men and 87 women; mean age 60 ± 13 years) who presented acute coronary syndrome with ST segment elevation and admitted in cardiology department of Hussein-Dey hospital (Algiers, Algeria), between 28th February 2014 and 16th August 2015.At emergency department admission, an ECG Holter recorder was attached for continuous ECG monitoring during 48 hours, the 17-leads surface ECG recorded at admission and repeated during hospitalization, Doppler Echocardiography, coronary angiography, and biological assessment were performed in the majority of patients.The most important rhythm and conduction disorders were identified, the patients with the same type of disorder are grouped together, and the name assigned to each group is that of the disorder that characterizes it; there are overlaps between the groups, so that several disorders may exist in the same patient.The constitution of each group of the rhythm disorder implies the constitution of the opposite group without the corresponding disorder, the latter group is used for the comparative study; each group is therefore described and then compared to the corresponding opposite group.In this sub study, the group of patients with nonsustained www.cmhrj.comventricular tachycardia was compared to the rest of patients without nonsustained ventricular tachycardia.

Statistical analysis:
Data are presented as mean ± SD, median, or frequency (percentage) where appropriate.Continuous variables were compared using the ANNOVA test, or H Kruskal Wallis test.χ2 tests and Fisher's exact test were performed to distinguish differences between categorical variables.Statistical significance was defined as p < 0.05.In this first step, we used EPI-info version 6.0.A multivariate Binary regression was performed to determine the predictor factors of arrhythmias, and Cox regression was performed to identify the predictor factors of mortality.The magnitude of the relationship between nonsustained ventricular tachycardia and their predictive factors is estimated by the Cramer V coefficient, a coefficient lower than 0.2 is in favor of a weak link, between 0.2 and 0.5: moderate link, greater than 0.5: strong link.The statistical analysis was performed using SPSS Statistics (release 17).

Incidence:
The characteristics of the 467 patients included in our study are shown in Table 1; 132 patients had presented nonsustained ventricular tachycardia at admission or during hospitalization, so its frequency in this present study is 28.Holter ECG was performed in all patients (132 patients); this exam had participated in the recording of NSVT, also showed its timing (early or late), morphology (monomorphic or polymorphic), rate (slow or fast), the number of episodes (isolated or recurrent).(Figure 1) (Figure 2) (Figure 3)   The magnitude of the relationship between NSVT and its predictive factors is low; the Cramer V coefficient does not exceed 0.2.(Table 4)

Discussion
Non-sustained ventricular tachycardia (NSVT) defined as ventricular tachycardia lasting less than 30 seconds; is one of the most frequent ventricular arrhythmias, Repetitive Non-Sustained Ventricular tachycardia may induce hemodynamic instability, and promotes the onset of cardiogenic shock during hospitalization.
Its mechanisms are complex and multifactorial; several electrophysiological modifications occur just after coronary artery occlusion, and lead to reentry phenomena, abnormal automaticity, and triggered activity.
In acute coronary syndrome, ischemia and reperfusion, cause profound ionic and metabolic changes in intra and extracellular.Ischemia causes alterations of the resting membrane potential and the action potential, these electrophysiological changes, induce arrhythmias by abnormal automaticity or reentry phenomena.[1][2] Biochemical and metabolic changes in reperfusion depend on the duration of ischemia; the mechanism of reperfusion arrhythmias is mainly the triggered activity.[2] Several international studies have reported the incidence of NSVT in acute coronary syndrome, this incidence varied between 1 to 7 %, [3][4][5] and be higher than 75 %.[6] According to Tatli et al, incidence of NSVT is about 57.5 %, [7]; in another study, the incidence of NSVT is 25.84 %, in patients treated by Primary Percutaneous Coronary Intervention (PCI) for ST-Segment Elevation Myocardial.[8] The incidence of NSVT in our study was 28.3 % (132 patients), CI 95% [24.2-32.4].This incidence is within the range of that reported in the literature, and similar to that reported in study that exclusively uses primary angioplasty, which proves that fibrinolytics are as effective as primary angioplasty, in coronary artery reperfusion.
Several studies have reported predictive factors of severe ventricular arrhythmias, but there are no specific studies about predictors of NSVT.
According to the Thai registry, predictive factors of ventricular arrhythmias are cardiogenic shock, tobacco, and elevated troponin levels [9] For the PAMI study, the predictors of severe ventricular arrhythmias are tobacco, TIMI flow 0, the right territory of the ACS, early consultation time, and non-administration of beta blockers early on admission [10] In another study published in 2012, the predictive factors of severe ventricular arrhythmias are the following: tobacco, taking beta blockers, digitalis and significant left main coronary artery disease [11] In our study, predictive factors of NSVT were studied separately, after multivariate analysis using binary logistic regression, the following predictive factors of NSVT are: Age ≤ 58 years, current active smoking, presence of akinetic segment, early consultation < 6 hours.The age of 58 years or younger, increases the risk NSVT (OR: 1.7), the occurrence of NSVT, assumes the absence of a permanent substratum like fibrosis, which may participle in the maintenance of ventricular tachycardia, so myocardium without pre-existing lesions, is the situation that frequently encountered in young subjects.Current active smoking, increases the risk of NSVT (OR: 1.9), an exclusively male risk factor in our population, nicotine stimulates the release of catecholamine, increased carbon monoxide, reduces the release of oxygen to cells, in addition to the abrasion of the endothelium and the reduction of prostaglandin production, all these effects contribute to artery coronary spasm and promote acute thrombosis causing severe electrophysiological changes.The Akinetic segment of myocardial walls, increases the risk of NSVT (OR: 2), reflects the significant damage caused by ACS, and allows initiation of NSVT.Short time from symptom onset to emergency room (Early consultation < 6 hours) (OR: 2.3), allows the administration of reperfusion treatment as soon as possible, and also start arrhythmias recording earlier.
We can therefore assume that NSVT is primarily related to reperfusion and triggered activity.
There have been some controversies about the risk of mortality associated with NSVT in ACS; in some studies, occurrence of NSVT is not associated with high risk mortality or sudden cardiac death, especially when NSVT occurred within the first 48 hours of ACS.[12][13] [14] www.cmhrj.com According to another study, only NSVT occurred late, after the first 12 hours in ACS, were associated with high risk of mortality.[15] In our study, in-Hospital mortality (first 48 hours), in the NSVT group is lower compared to the opposite group without NSVT, the percentage mortality in the NSVT is about 0.75 % while it exceeds 4.77 % in the group without NSVT, p = 0.024.(HR at 0.156, CI 95% [0.21-1.177],p = 0.072.Our results support the conclusions of most studies, which assume the benign character of these arrhythmias.

Conclusion:
Non-Sustained Ventricular Tachycardia (NSVT) is one of the most frequent ventricular arrhythmias in acute coronary syndrome with ST segment elevation.Its predictive factors according to our study are: Age ≤ 58 years, current active smoking, presence of akinetic segment in echocardiography, and early consultation.The occurrence of NSVT doesn't increase the risk of hospital mortality, this result support the conclusions of most studies.
To our knowledge, predictors of non-sustained ventricular tachycardia were reported for the first time.

Figure 1 :Figure 2 :Figure 3 :
Figure 1: Holter ECG showed acute coronary syndrome with ST segment elevation complicated with monomorphic Non Sustained Ventricular Tachycardia in the first two hours of recording