Abstract score. Basal and 3 months follow

Abstract

Background:
Following
acute ST elevation myocardial infarction (STEMI), restoration of large-vessel
patency does not mean complete perfusion recovery, and perfusion of the
microvasculature is an additional prerequisite for obtaining optimal recovery (1).
QRS score appears to be important in the early risk stratification for STEMI (2). QRS score derived from simple
and widely available electrocardiogram (ECG) may be a useful parameter for
assuring the presence of microvascular obstruction (3).

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Aim of the work: The aim of this
clinical study is to validate the 90 minutes modified Selvester  QRS score reduction as a reliable predictor of
myocardial salvage, represented by 3 months global longitudinal strain (GLS)
value, following successful reperfusion of acute STEMI.

Material/Methods:
The study
population included 400 patients presented with first acute STEMI with
successful reperfusion by thrombolysis (Group I- 200 patients: mean age=57.1 ± 11.6
years) or primary percutaneous intervention (PPCI) (Group II- 200 patients: mean
age=58.2±9.8 years). Basal and 90 minutes after reperfusion electrocardiography
was done with assessment of ST resolution and modified Selvester QRS score. Basal
and 3 months follow up echocardiography was performed with assessment of
ejection fraction (EF) and GLS as an indicator for myocardial salvage with its
impact on long-term clinical outcome.  

Results:  90 minutes ST resolution and QRS score
reduction were significantly higher in PPCI group (P.: 0.04*, 0.03*). Patients
in group I had non-significant improvement of EF (P.: 0.22) during follow-up,
but highly significant improvement of GLS (P.: ?0.001**) compared to the basal
echocardiographic study. Patients in group II had significant improvement of EF
(P.: 0.01*) during follow-up, and highly significant improvement of GLS (P.:
?0.001**) compared to the basal echocardiographic study. As regarding
correlation with 3 months GLS value, there was highly significant negative
correlation between 3months GLS and (ST resolution and QRS score reduction)
(P.: ?0.001**). Receiver operating characteristics (ROC) curve analysis shows
that 90 minutes QRS score reduction has the best cut off value of 70% to
predict 3months GLS improvement with 80% sensitivity and 79% specificity.

Conclusions:
Modified Selvester
QRS score reduction 90 minutes after reperfusion is a cheap bedside ECG
parameter added to ST resolution, can be considered as a reliable predictor of
future myocardial salvage with its impact on long-term clinical outcome and
modifying management strategies.

Keywords:  Modified Selvester QRS score • Myocardial
infarction• Myocardial salvage

 

Corresponding author: Islam Ghanem Ahmed
Ghanem,01100224180, 01001270412. [email protected]

·        
Introduction: –

Following
revascularization of acute STEMI patients, despite the restoration of
large-vessel flow, tissue perfusion in the area at risk frequently continues to
be compromised. Persistent microcirculatory impairment is associated with poor
recovery of contractile function and adverse clinical outcomes. Thus,
restoration of large-vessel patency does not mean complete perfusion recovery,
and perfusion of the microvasculature is an additional prerequisite for
obtaining optimal recovery (1).

The modified
Selvester QRS score (Table 1) based on ECG criteria capable of generating a
total of 29 points with each point in the score corresponding to 3% of the left
ventricular (LV) mass (4).

Global longitudinal strain (GLS)
is considered an effective parameter for quantifying left-ventricular function
more sensitive than LV ejection fraction (EF) assessed by two-dimensional (2D)
echocardiography and their role in large MI has been previously reported (5),
even in patients with a relatively preserved LV function after acute MI (6).
Vartdal et al. (2007) (7) showed that global peak negative
strain correlated well with final LV infarct size in patients with AMI.

Global longitudinal strain (GLS) is calculated as the
average of the observed segmental values of peak LS from the three apical views
(8). GLS measures less than (-20%) is considered abnormal (9).

The aim of this
clinical study is to validate the 90 minutes modified Selvester QRS score reduction
as a reliable predictor of myocardial salvage, represented by 3 months GLS
value, following successful reperfusion of acute STEMI.

·        
Subjects
and methods: –

§ 
Study
design and population:

     This clinical study included 400 patients
with first time acute STEMI who were admitted to the coronary care unit (CCU)
and cathlab. units of cardiology department at Zagazig University, Egypt and
Kaohsiung Chang Gung Memorial Hospital, Taiwan during the period from November
2015 to November 2017.

§ 
 Inclusion
criteria of the study:  

We included
patients who were admitted with first acute STEMI with successful reperfusion either
by PPCI or thrombolytic therapy.

§ 
Exclusion
criteria of the study:

·        
Failed reperfusion or
revascularization.

·        
History of myocardial
infarction.

·        
History of previous PCI or coronary
artery bypass graft (CABG).

·        
 History of heart muscle diseases
(cardiomyopathies).

·        
History of significant valvular
diseases.

·        
Significant arrhythmias
(including atrial fibrillation and frequent extra-systoles).

·        
Previous pacemaker or
cardioverter-defibrillator implantation.

·        
Very poor image quality.

 

§ 
Ethical consideration:

Consent was obtained from every patient after explanation of the
procedure. Medical research and ethics committee approved the study.

§ 
Patient
groups:

We
categorized patients into 2 groups:

Group I (200 patients): Patients with
first acute STEMI with successful reperfusion by thrombolytic therapy.

Group II (200 patients): Patients with
first acute STEMI with successful reperfusion by PPCI.

Successful
reperfusion was documented by more than 70% resolution of ST segment elevation
90 minutes after revascularization (10)

§ 
Data collection:

Data were
collected for all patients including:

§  Complete
history taking: Including name, age, gender, special habits, menstrual
state, drug history and previous hospital admission with special consideration
to history of risk factors to ischemic heart disease (Hypertension: HTN, diabetes
mellitus: DM, smoking, dyslipidemia) and co-morbid conditions.

§  Thorough
clinical examination: All patients were subjected to thorough clinical general and
local cardiac examination with special emphasis on hypotension and elevated
jugular venous pulse in the presence of clear lung fields.

·        
Electrocardiography (ECG):

ECG machine
(BTL-08 SD1, BTL Industries Inc., USA and MAC 5500 GE Healthcare
MUSE v8, USA) was used to record standard 12-lead ECGs. They were recorded at a
paper speed of 25 mm/ second (s) and a gain of 10 mm/mv.  

Twelve-lead ECG was performed directly
before and 90 min after reperfusion. We analyzed the sum of elevations of ST
segments in all leads and the modified Selvester QRS
score (Table 1) based on ECG criteria capable of generating a total of 29
points with each point in the score corresponding to 3% of the left ventricular
(LV) mass.

 

·        
Echocardiography:

           Resting
transthoracic echocardiography was performed for all patients using the Vivid 9
system (GE Vingmed Ultrasound AS, Horten, Norway). Images were taken while the
patient is supine or in left lateral position Three apical scans of the left
ventricle in the three-chamber, four-chamber, and two-chamber views with ECG
triggering according to the guidelines of the American Society of
Echocardiography were performed (12).
Two examinations were done, the first is immediately after reperfusion and the
second is 3 months later.

The following
measurements were taken:

(A) 
 Ejection fraction (EF): The LV volumes
and ejection fraction (EF) were determined using the modified Simpson biplane
technique from the apical 4- and 2-chamber views.

           It is calculated also from the
formula:

           EF= (EDV- ESV)
? EDV ×100

           Normally it is
50 – 70 % (13).

(B)  
Strain
echocardiography (STE) using the speckle tracking technique:

                       STE is an echocardiographic, non-Doppler
method that analyzes the longitudinal strain (LS) of LV segments by assessing
the deformation of an object relative to its original length. STE is performed
in typical apical views with frame rate of 60 to 90 frames/sec, and strain will
be automatically measured. The technique of strain measurement requires
manually outlining the LV endocardial contour
then the software analyzed the speckles within the myocardium and calculates
the segmental strain, and afterward, the system automatically generates
myocardial contour in the late systolic phase. Patients in whom more than four
segments can’t be analyzed will be excluded. The system generates curves of LS
for each segment of the left ventricle, from which we estimate peak
longitudinal strain (LS) during the cardiac cycle. Peak systolic strain was
defined as the peak negative strain value during systole (14).

 Global LS (GLS) is
calculated as the average of the observed segmental values of peak LS from the
three apical views (8).
GLS measures less than (-20%) is considered abnormal (9).

·        
Reperfusion of acute STEMI:

Reperfusion of
acute STEMI was done in all patients using thrombolytic therapy or primary PCI.
Primary PCI was done using femoral or radial access. Imaging the non-infarct
related artery (non-IRA) was done first. Then, IRA angiogram was done, thrombus
aspiration and glycoprotein IIb-IIIa inhibitors infusion was done in high
thrombus burden lesions. TIMI III flow, grade III myocardial blush and
corrected TIMI frame count (CTFC) less than 27 were achieved in all patients.

Statistical analysis

Data
were then imported into Statistical Package for the Social Sciences (SPSS
version 20.0) software for analysis. Quantitative data were expressed as means±
SD and qualitative data were expressed as absolute frequencies (number) & relative frequencies (percentage). Differences between
means in two parametric groups were compared by Student’s t test.
Non-parametric data by Chi-square test. Bivariate correlation was used to study
association between two continuous variables. Multivariate Logistic regression
analysis was used to detect independent predictor of certain parameter. P value
was set at <0.05 for significant results & <0.001 for high significant results (15). Results In our study, we enrolled 400 patients with first time acute STEMI who were admitted to the coronary care unit (CCU) and cathlab. units of cardiology department at Zagazig University, Egypt and Kaohsiung Chang Gung Memorial Hospital, Taiwan during the period from November 2015 to November 2017.   As regarding demographic data and risk Factors, there was non-significant difference between patients of both groups regarding age (P.: 0.42) and gender (P.: 0.27). Also, there was non-significant difference between both groups regarding the risk factors of coronary artery disease like hypertension (P.: 0.51), diabetes mellitus (P.: 0.33) and smoking (P.: 0.38). But there was significant statistical difference between both groups regarding dyslipidemia (P.: 0.01). As regarding ECG data, 90 minutes ST resolution and QRS score reduction were significantly higher in PPCI group (P.: 0.04*, 0.03*). As regarding echocardiographic data, patients in group I had non-significant improvement of EF (P.: 0.22) during follow-up, but highly significant improvement of GLS (P.: ?0.001**) compared to the basal echocardiographic study. Patients in group II had significant improvement of EF (P.: 0.01*) during follow-up, and highly significant improvement of GLS (P.: ?0.001**) compared to the basal echocardiographic study. As regarding correlation with 3 months GLS value, there was highly significant negative correlation between 3mo. GLS and ST resolution (Figure 1) and QRS score reduction (Figure 2) (P.: ?0.001**). ROC curve analysis shows that 90 minutes QRS score reduction has the best cut off value of 70% to predict 3months GLS improvement with 80% sensitivity and 79% specificity (Figure 3).   Discussion QRS score appears to be important in the early risk stratification for STEMI (2). The presence of high QRS score is an independent predictor of incomplete ST recovery and 30-day MACE in STEMI treated with primary PCI (16). Assessment of infarct size by echocardiography after PCI in patients with STEMI was superior with GLS when compared with LVEF. Since global strain is an inexpensive test, these data may be of health economic interest (17). Our study showed that there was non-significant difference between patients of both groups regarding age (P.: 0.42) and gender (P.: 0.27). Also, there was non-significant difference between both groups regarding the risk factors of coronary artery disease like hypertension (P.: 0.51), diabetes mellitus (P.: 0.33) and smoking (P.: 0.38), but significant regarding dyslipidemia (higher in thrombolysis group) (P.: 0.01). Thus, our sample population is to an extent matched. we can notice that among our sample size, Taiwanese population had less incidence of dyslipidemia compared to Egyptian population. We attribute that to less caloric diet, more exercise program adoption and heathier lifestyle. Our study showed that 90 minutes ST resolution was significantly higher in PPCI group (P.: 0.04*) and this is in agreement with Rahman et al., 2016 which reported that ST-segment resolutions were significantly more in PPCI than thrombolysis at 90 minutes (73.15±18.76 vs 60.06±23.33%, p<0.015) (18). Our study showed that 90 minutes QRS score reduction was significantly higher in PPCI (P.: 0.03*). Abdel-Salam et al., 2010 reported that the mean QRS score was significantly lower in the ST resolution group compared to the non-resolution group (2.88 +/- 1.34 vs 5.93 +/- 1.56, respectively, p < 0.001) (19). Our results showed that, there was non-significant difference between echocardiographic parameters of the studied groups during the acute STEMI (P.: 0.08 for basal EF and 0.2 for basal GLS, however all parameters in both groups denote impaired systolic and diastolic LV function during acute STEMI (Stunning). Early assessment of LV-EF after acute MI can be misleading (20) because it is affected by the presence of myocardial stunning, thus it may not distinguish viable from nonviable myocardium (21). But the follow-up parameters showed more significant improvement of LV function in PPCI group (P.: 0.02* for 3mo. EF, ?0.001** for 3mo. GLS). Similar results were reported by Ottervanger et al.,2001 (22). Left ventricular GLS as measured by 2D speckle tracking echocardiography immediately after primary PCI has also been shown to be an excellent predictor of adverse LV remodeling and cardiac events in patients with acute myocardial infarction. As compared to LVEF, GLS has the advantage of minimal inter-observer variability (23). Liszka et al., 2014 suggested that impaired indices of LV deformation detected 3 days and 30 days after AMI may provide important predictive value in LV remodeling and patients' follow-up (24). Our results showed highly significant negative correlation between 3months GLS and (ST resolution and QRS score reduction) (P.: ?0.001**).  The absence of ST-segment elevation resolution after PCI was also associated with a lack of left ventricular function recovery. Numerous studies from the fibrinolytic era have found that the absence of ST-segment elevation resolution after reperfusion has been associated with poor outcomes, including larger infarct size and increased mortality (25). This is in agreement with Watanabe et al., 2015 who indicated that the QRS score derived from simple and widely available ECG may be a useful parameter for assuring the presence of microvascular obstruction (3). ROC curve analysis shows that 90 minutes QRS score reduction has the best cut off value of 70% to predict 3months GLS improvement with 80% sensitivity and 79% specificity (Figure 3).  It may be argued that the primary outcome is a surrogate marker rather than a hard clinical endpoint. However, in a carefully selected cohort of low-intermediate risk STEMI patients in which hard outcome variables such as in-hospital mortality and morbidity were negligibly low, LV systolic function recovery represented by 3 months GLS improvement exemplifies a valid surrogate endpoint to detect the differences in outcomes of the treatment strategies adopted.   Conclusions GLS measurement (compared to EF) early after STEMI is a reliable predictor for myocardial functional recovery assessed 3 months later, which surely would be expressed on the clinical outcomes. PPCI leads to better myocardial salvage compared with fibrinolysis. Modified Selvester QRS score reduction 90 minutes after reperfusion is a cheap bedside ECG parameter added to ST resolution, can be considered as a reliable predictor of future myocardial salvage with its impact on long-term clinical outcome and modifying management strategies. Limitations Due to low event rate in selected low-intermediate risk STEMI patient, we couldn't rely on major adverse cardiac event (MACE) as a hard clinical endpoint to validate the QRS score for prediction of long-term outcomes. Conflict of interest None.