Prognostic value of ST segment in aVR lead in non-ST
segment elevation acute coronary syndrome.
RICARDO A. GARCÍA HERNÁNDEZ, LIANET RIVERO SERIEL
Hospital de Rehabilitación Julio Díaz, Hospital Clínico-Quirúrgico Hermanos Ameijeiras.
(19815) Fontanar, La Habana, Cuba. E-mail
Recibido 21-MAR-2018 – ACEPTADO despues de revisión el 17-ABRIL-2018.
There are no conflicts of interest to disclose.
Introduction: Recently it has been suggested that lead aVR on standard electrocardiogram may provide prognostic information in patients with non-ST segment elevation acute coronary syndrome. Objective: To evaluate the contribution of ST segment in lead aVR and the occurrence of cardiovascular death and in-hospital recurrence at 1-year follow-up. Methods: Observational, analytic prospective study in patients with Non-ST segment elevation acute coronary syndrome hospitalized in Coronary Care Unit at Hospital Enrique Cabrera from 02-05-2015 to 08-05-16. According to the ST segment in lead aVR, patients were divided into 3 groups. Multivariate analysis was performed. Results: 65 years and more (52.3%), white skin and male sex (69.5% and 61.4% respectively) with more than two comorbidities (56.8%) and Killip-Kimball class I (85.3%) were predominant. An increase in cardiovascular mortality and in-hospital recurrence at 1-year follow-up was observed in the ST segment elevation (lead aVR) group (18.9% and 35.2% [p=0.00]). Conclusion: ST segment elevation in lead aVR was a strong predictor of cardiovascular death and in-hospital recurrence in 1-year follow up (p=0.00 ˂0.05).
Atherosclerosis and its main organic consequences –ischemic heart disease (IHD), cerebrovascular disease, peripheral arterial occlusive disease and atherosclerotic aneurysms- are considered from the epidemiological point of view, as the first cause of death in countries where infections do not hold a preponderant position, and in them, it constitutes the first cause of morbidity [1,2]. The main form of presentation of an acute ischemic event is constituted by acute coronary syndromes (ACS), which are responsible for more than a third of deaths in western countries .
According to registry data, non-ST segment elevation acute coronary syndrome (NSTE-ACS) is more frequent in regard to ST-segment elevation acute coronary syndrome (STE-ACS); with the latter presenting a higher in-hospital mortality than NSTE-ACS; although in the long term, the rate of death of the latter is greater, which could be due to NSTE-ACS per se being an expression of unstable coronary artery disease (CAD), prone to ischemic recurrence and other complications, which may lead to acute myocardial infarction (AMI) or death in the short and long term .
In order to predict the appearance of these complications, numerous significant predictors arose in clinical practice. Recently, ST-segment analysis in lead aVR became important, which has been associated to a high probability of severe CAD, as well as a worse clinical prognosis [5,6,7].
To analyze ST-segment variation in lead aVR in patients with NSTE-ACS in relation to the occurrence of death or hospital readmission by cardiac cause, in the term of 1 year.
To characterize patients according to clinical and sociodemographic variables.
To evaluate the association between ST segment in aVR and the clinical variables being studied.
To evaluate the association between ST segment in aVR and the occurrence of death and hospital readmission over 1 year, regardless of risk factors known for these patients.
MATERIAL AND METHODS
An observational, longitudinal, prospective study was conducted in patients admitted into the Coronary Care Unit of the Hospital Clínico-Quirúrgico “Enrique Cabrera”, with diagnosis of NSTE-ACS during the term from May 2015 to May 2016. There were 495 patients studied. In each case, a 12-lead ECG was performed at the time of hospital admission, and according to the ST segment in lead aVR, the universe in study was divided into three groups: those presenting ST-segment elevation, those presenting ST-segment depression, and those that did not show ST-segment alteration in the mentioned lead. The occurrence of adverse cardiovascular events was also assessed from the beginning of the study and for 1 year of follow-up, defined as death or hospital readmission by cardiac cause, obtaining this information during medical consultation with patients or their relatives. Sociodemographic, clinical, angiographic and electrocardiographic variables were studied.
The individual data of each patient were obtained from the clinical histories during admission, which were inserted and processed in a database created for this purpose. Contingency tables were prepared using X2 test. A survival curve was prepared, using the Kaplan-Meier method, besides using a multivariate logistic regression model.
The population of the study included 495 patients according to the variation of ST segment in lead aVR, who were distributed into 3 groups: elevation group (ELV) with 332 patients (67.0%); depression group (DPS) with 105 patients (21.2%); and the group with no variations (NV) with 58 patients (11.8%).
In the ELV and DPS arms, patients predominated in the group with 65 years and older, in 59.0 and 41.0%, with an average age of 63.6 and 58.3 years respectively. In the NV arm, patients between 25-59 years predominated, in 50% and average age of 56.1 years (Table 1).
Table 1. Distribution of patients by the groups of the study, according to age, gender and race
ST SEGMENT IN aVR
X2 = 21.62
p = 0.000*
63.6 ± 7.4
58.3 ± 5.7
61.6 ± 8.3
X2 = 11.18
p = 0.004*
p = 0.368
Source: Data collection spreadsheet. *: Significance (p<0.05) - ELV: Elevation; DPS: Depression; NV: No variation.
About gender, it was found that the male gender was the one with higher predominance in patients that presented ST-segment variation in aVR. For those with ELV, it was 61.1% and for those that presented DPS 71.4%. As to the NV arm, the female gender was the most frequent one, representing 55.2%. Caucasians predominated in the three study groups, with ELV (67.5%), with DPS (74.3%) and NV (72.4%).
It was possible to verify that the patients that had more than two diseases associated were the most frequent ones in the groups that presented ST-segment variation in aVR. For those who had ELV, it was 61.4% and those with DPS, 54.3%. However, in those with no variation in the segment, HTN was the most frequent pathological background, representing 37.9%. (Table 2)
Table 2. Distribution of patients by study groups according to personal pathological history and Killip-Kimball class.
ST SEGMENT IN aVR
Previous myocardial infarction
2 or more
Source: Data collection spreadsheet. X2 = 36,7; p=0.000 <0.05 - ELV: Elevation; DPS: Depression; NV: No variation.
In Figure 1, the occurrence of death and hospital readmission is shown in the term of 1 year, in relation to the ST segment in aVR. In the ELV arm, there was a predominance of patients that died (18.9%) in relation to the rest of the groups of study (1.9 and 1.7% respectively). Likewise, it was observed that the highest frequency of patients who were readmitted in hospitals by cardiovascular cause corresponded to the ELV group (35.2%). (Tabla 3)
Figure 1. Occurrence of death and hospital readmission in 1 year in regard to ST segment in aVR.
Table 3. Linear logistic regression analysis for death and hospital readmission
Personal pathological history
As it can be seen in Figure 2, in the group presenting ELV, the tendency was that as the shift advanced in a positive sense for ST in lead aVR, the number of deceased patients (A) and hospital readmissions (B) increased. In Figure 3, in one year of follow-up, a lower survival was observed in patients presenting ELV in the ST segment in aVR for 10.1 months. When compared by Log Rank, the difference between groups was statistically significant (p=0.00, <0.05).
Both ELV (aVR) [p=0.00] and Killip-Kimball class (p=0.00) were the variables significantly influencing mortality and hospital readmission by cardiovascular cause.
Figure 2. Tendency to death and hospital readmission in regard to ST segment magnitude and variation in aVR.
Figure 3. Survival in the groups of the study.
As it was possible to verify, there was a predominance of patients in the range of ages from 65 years and older, and this finding was the expected one taking into account that the prevalence of NSTE-ACS increases in a quick progression with age. Other authors have already reported results similar to those in this study [8,9,10]; however, in other studies a greater prevalence of NSTE-ACS was verified in the range of ages above 70 years, which could be explained from the overall and increasing tendency of population ageing. Thus, the population of 25-74 years increased only by 15%; while the 75-year old and older population has increased by 34% . On the other hand, it was verified that male gender was the most prevalent one, a result coinciding with what was reported in other studies [10,12,13].
In this study, white patients predominated, which could be due to the composition of the Cuban population, according to data from the population census, which is mainly white ; although we should emphasize that the prevalence of CAD is usually greater in non-white individuals, in whom the complications attributable to coronary atherosclerosis are also more frequent .
We should highlight that in this study, patients with more than 2 associated diseases predominated. These results were also expected, taking into account that most of the patients involved had a more advanced age, which is generally associated to a greater co-morbidity and propensity to presenting NSTE-ACS . We should also point out that hypertension (HTN) was the most frequent isolated pathological event, a condition that agrees both with global and territorial statistics [16,17].
As to the Killip-Kimball (KK) class, stage I predominated in study groups, which is understandable taking into account that in a scenario of NSTE-ACS, the culprit artery for the acute ischemic episode does not present total occlusion of its lumen, so regularly clinical manifestations are not as severe as in ST-segment elevation acute myocardial infarction (STEMI) [18,19]. The patients in the ELV group presented more advanced KK stages when compared to the rest of the groups of the study.
KK classification has been widely studied in patients with STEMI and multiple risk factors, where the presence of more severe CAD manifests, with greater extension of the ischemic process [20,21]. This study, however, was conducted in patients who presented NSTE-ACS, where the group of patients that presented ELV (with more advanced KK stages) presented clinical characteristics of risk similar to the patients in the previously mentioned studies.
It was possible to observe that in the group of patients that presented ELV, there was a greater number of deceased patients and higher hospital readmission in comparison to the rest of the study groups. A report by Ferreira-González  has shown the association existing between ST-segment variation in aVR and in-hospital mortality in patients with NSTEMI. Taglieri et al, however proposed that the occurrence of death and hospital readmission is usually greater in patients that present simultaneously ST-segment depression in more than one electrocardiographic lead and ST-segment elevation in aVR .
This study could verify that there is a linear relationship between ST-segment elevation in aVR and the appearance of adverse cardiovascular events, a fact matching the findings in other studies [6,23]. In one year of follow-up, we observed that survival free from events was lower in the ELV group in regard to the rest of the groups of the study, which could be justified as these patients had more advanced ages, worse Killip-Kimball functional class and greater number of co-morbidities.
This study presents the biases proper of observational studies. Another of the main limitations of this study is that it was conducted in a single hospital, to which we should add the small number of cases. Moreover, we should emphatically highlight that troponins were not used due to lack of resources and not having them available.
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