Abstract
Background
We sought to explore the prognostic power of certain patient characteristics to predict myocardial contractile recovery after coronary revascularization in patients with prior myocardial infarction.
Methods and Materials
We enrolled 100 consecutive patients with prior myocardial infarction, significant coronary stenosis/occlusion amenable for revascularization, and regional wall motion abnormality in the distribution of the affected artery. All patients underwent echocardiographic assessment of regional wall motion and left ventricular ejection fraction. Patients underwent coronary revascularization by either percutaneous angioplasty or surgical bypass. Echocardiography was repeated 8 weeks following revascularization. Patients were classified into two groups: Group 1 with evidence of contractile improvement after revascularization at follow-up echocardiography and Group 2 with no such evidence of improvement. The two groups were compared with respect to patients’ clinical characteristics and echocardiographic and angiographic data.
Results
Predictors of contractile recovery after revascularization included angina pectoris, the shorter age of infarction at the time of revascularization, a higher baseline left ventricular ejection fraction, a lower baseline wall motion score index, the presence of Grade 2–3 collaterals to the infarct-related artery, and the absence of dyspnea or diabetes mellitus. Stepwise regression analysis identified the presence of Grade 2–3 collaterals to the infarct-related artery and the age of infarction at the time of revascularization as independent predictors of contractile recovery after revascularization.
Conclusions
In patients with prior myocardial infarction, the presence of Grade 2–3 collaterals to the infarct-related artery and the shorter age of infarction at the time of revascularization independently predicted myocardial contractile recovery after coronary revascularization.
1
Introduction
With the enormous progress in the field of myocardial revascularization over the last two decades, predicting the presence of viable myocardium has acquired paramount clinical importance, particularly in patients considered for interventional treatment . Myocardial viability represents impairment in contractile function that is potentially reversible if blood supply is adequately restored . Presumably, improving blood supply to dysfunctional but viable regions results in subsequent improvement of regional and global left ventricular function, heart failure symptoms, functional capacity, and long-term survival. Thus, an important question is whether hypokinetic or akinetic myocardial areas represent viable myocardium with critically jeopardized blood supply or irreversibly necrotic scar tissue . This scenario was supported by the results of several studies where only patients with severe left ventricular dysfunction who harbored viable myocardium gained benefit from revascularization . In a prospective study design, we sought to explore the prognostic power of certain patient characteristics to predict potential contractile recovery after revascularization in patients with prior myocardial infarction.
2
Patients and methods
2.1
Population
We included 100 consecutive patients referred from our catheterization labs with significant coronary stenosis/occlusion, during the period from January 2004 to December 2007. Patients were considered eligible for inclusion if they had regional wall motion abnormality in the anatomical distribution of the affected artery as explained later, an affected artery amenable for revascularization, and evidence of prior myocardial infarction more than 3 months before study enrollment. Significant coronary stenosis was defined as at least 70% luminal obstruction of at least one sizable coronary artery (measuring 2.5 mm or more in diameter), seen in 2 different projections. Coronary occlusion was defined as 100% luminal obstruction with Thrombolysis In Myocardial Infarction Grade 0 forward flow distal to the site of obstruction. Prior myocardial infarction was defined based on 12-lead electrocardiogram showing abnormal Q waves (≥1 mm in width) in at least two contiguous leads or lab evidence of elevated cardiac biomarkers: CK-MB and/or troponin more than twice the upper limit of normal lab reference. We excluded patients with post-infarction unstable angina or severe hemodynamic instability, significant valvular or congenital heart disease, any myocardial disease apart from ischemia, left ventricular ejection fraction >45%, and patients with limited life expectancy due to coexistent disease (e.g., malignancy). Before inclusion, an informed consent was obtained from each patient, and the study protocol was reviewed and approved by our local institutional human research committee as it conforms to the ethical guidelines of the 1975 Declaration of Helsinki.
2.2
Definitions of risk factors
The presence of hypertension was defined as systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg, previously recorded by repeated noninvasive office measurements, which lead to lifestyle modification or antihypertensive drug therapy. The presence of diabetes mellitus was defined as fasting plasma glucose ≥126 mg/dl, and/or 2-h post glucose load ≥200 mg/dl, or specific antidiabetic drug therapy. Dyslipidemia was defined as LDL cholesterol >100 mg/dl, and/or serum triglycerides >150 mg/dl, and/or HDL cholesterol <40 mg/dl and <50 mg/dl in women.
2.3
Methods
Assessment of regional and global left ventricular systolic function was performed in all patients by tarns-thoracic echocardiography within 48 h of admission. Doppler echocardiography was performed using a Hewlett Packard Sonos 5500 cardiac ultrasound machine (Hewlett Packard, Andover, MA, USA) equipped with harmonic imaging capabilities. A 2.5-MHz phased array probe was used to obtain standard 2D, M-mode, and Doppler images. Patients were examined in the left lateral recumbent position using standard parasternal and apical views. Images were digitized in cine-loop format and saved for subsequent playback and analysis. Views were analyzed by a single echocardiographer employing the software program of the echocardiography machine. Global left ventricular systolic function was assessed in apical four-chamber view using the modified Simpson’s rule. Regional wall motion was assessed according to the standard 16-segment model recommended by the American Society of Echocardiography . Individual segments were then subgrouped based on the known vascular distribution into left anterior descending territory, left circumflex territory, right coronary artery territory, and overlap segments . Regional wall motion was visually assessed for each segment individually, considering both endocardial excursion and systolic thickening, and each segment was graded according to the semiquantitative scoring system described by Knudsen et al . Segments with poorly defined endocardial borders for 50% or more of their length were considered nonvisualized and assigned a score of 0 . Wall thickening was assessed at a distance of at least 1 cm from the adjacent segment to minimize the effect of tethering . Wall motion in a vascular territory was considered abnormal if wall thickening was abnormal in at least two contiguous nonoverlap segments . Wall motion score index (WMSI) was derived by dividing the sum of individual segment scores by the number of interpretable segments.
2.4
Coronary revascularization
All patients underwent successful complete coronary revascularization either by percutaneous coronary angioplasty or by surgical bypass grafting, according to the decision of the attending physician. The decision was based on the clinical presentation, coronary anatomy, and evidence of ischemia.
2.5
Echocardiographic follow-up
Follow-up echocardiographic reassessment was performed 8 weeks after revascularization to evaluate regional and global left ventricular systolic function as described before. Evaluations were performed offline by the same echocardiographer who was blinded to both clinical and angiographic data. The presence of contractile recovery was defined by improvement of regional wall motion score by at least one grade in at least two contiguous nonoverlap segments along with at least 20% reduction in global WMSI compared with baseline evaluation . During follow-up, patients were interrogated for the occurrence of new myocardial infarction or congestive heart failure by clinical visits, telephone calls, hospital chart reviews, or personal communication with the referring physician.
2.6
Statistical analysis
All continuous variables were presented as mean±S.D., if they were normally distributed. Differences in the normally distributed variables were assessed using the t test and the paired t test for dependent variables. Categorical variables were described with absolute and relative (percentage) frequencies. According to the above definition of contractile recovery, patients were classified into two groups: Group 1 with evidence of actual contractile improvement after revascularization at follow-up echocardiography and Group 2 with no such evidence of improvement. The two groups were compared with respect to patients’ clinical characteristics, and baseline echocardiographic and angiographic data, using the unpaired t test for continuous and the Pearson’s χ 2 test for categorical variables. Twenty cases were randomly selected for analysis of intraobserver variability. Assessment of variability was performed using linear regression analysis. A probability value of P <.05 was considered statistically significant. Analyses were performed with SPSS version 12.0 statistical package (SPSS, Chicago, IL, USA).
2
Patients and methods
2.1
Population
We included 100 consecutive patients referred from our catheterization labs with significant coronary stenosis/occlusion, during the period from January 2004 to December 2007. Patients were considered eligible for inclusion if they had regional wall motion abnormality in the anatomical distribution of the affected artery as explained later, an affected artery amenable for revascularization, and evidence of prior myocardial infarction more than 3 months before study enrollment. Significant coronary stenosis was defined as at least 70% luminal obstruction of at least one sizable coronary artery (measuring 2.5 mm or more in diameter), seen in 2 different projections. Coronary occlusion was defined as 100% luminal obstruction with Thrombolysis In Myocardial Infarction Grade 0 forward flow distal to the site of obstruction. Prior myocardial infarction was defined based on 12-lead electrocardiogram showing abnormal Q waves (≥1 mm in width) in at least two contiguous leads or lab evidence of elevated cardiac biomarkers: CK-MB and/or troponin more than twice the upper limit of normal lab reference. We excluded patients with post-infarction unstable angina or severe hemodynamic instability, significant valvular or congenital heart disease, any myocardial disease apart from ischemia, left ventricular ejection fraction >45%, and patients with limited life expectancy due to coexistent disease (e.g., malignancy). Before inclusion, an informed consent was obtained from each patient, and the study protocol was reviewed and approved by our local institutional human research committee as it conforms to the ethical guidelines of the 1975 Declaration of Helsinki.
2.2
Definitions of risk factors
The presence of hypertension was defined as systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg, previously recorded by repeated noninvasive office measurements, which lead to lifestyle modification or antihypertensive drug therapy. The presence of diabetes mellitus was defined as fasting plasma glucose ≥126 mg/dl, and/or 2-h post glucose load ≥200 mg/dl, or specific antidiabetic drug therapy. Dyslipidemia was defined as LDL cholesterol >100 mg/dl, and/or serum triglycerides >150 mg/dl, and/or HDL cholesterol <40 mg/dl and <50 mg/dl in women.
2.3
Methods
Assessment of regional and global left ventricular systolic function was performed in all patients by tarns-thoracic echocardiography within 48 h of admission. Doppler echocardiography was performed using a Hewlett Packard Sonos 5500 cardiac ultrasound machine (Hewlett Packard, Andover, MA, USA) equipped with harmonic imaging capabilities. A 2.5-MHz phased array probe was used to obtain standard 2D, M-mode, and Doppler images. Patients were examined in the left lateral recumbent position using standard parasternal and apical views. Images were digitized in cine-loop format and saved for subsequent playback and analysis. Views were analyzed by a single echocardiographer employing the software program of the echocardiography machine. Global left ventricular systolic function was assessed in apical four-chamber view using the modified Simpson’s rule. Regional wall motion was assessed according to the standard 16-segment model recommended by the American Society of Echocardiography . Individual segments were then subgrouped based on the known vascular distribution into left anterior descending territory, left circumflex territory, right coronary artery territory, and overlap segments . Regional wall motion was visually assessed for each segment individually, considering both endocardial excursion and systolic thickening, and each segment was graded according to the semiquantitative scoring system described by Knudsen et al . Segments with poorly defined endocardial borders for 50% or more of their length were considered nonvisualized and assigned a score of 0 . Wall thickening was assessed at a distance of at least 1 cm from the adjacent segment to minimize the effect of tethering . Wall motion in a vascular territory was considered abnormal if wall thickening was abnormal in at least two contiguous nonoverlap segments . Wall motion score index (WMSI) was derived by dividing the sum of individual segment scores by the number of interpretable segments.
2.4
Coronary revascularization
All patients underwent successful complete coronary revascularization either by percutaneous coronary angioplasty or by surgical bypass grafting, according to the decision of the attending physician. The decision was based on the clinical presentation, coronary anatomy, and evidence of ischemia.
2.5
Echocardiographic follow-up
Follow-up echocardiographic reassessment was performed 8 weeks after revascularization to evaluate regional and global left ventricular systolic function as described before. Evaluations were performed offline by the same echocardiographer who was blinded to both clinical and angiographic data. The presence of contractile recovery was defined by improvement of regional wall motion score by at least one grade in at least two contiguous nonoverlap segments along with at least 20% reduction in global WMSI compared with baseline evaluation . During follow-up, patients were interrogated for the occurrence of new myocardial infarction or congestive heart failure by clinical visits, telephone calls, hospital chart reviews, or personal communication with the referring physician.
2.6
Statistical analysis
All continuous variables were presented as mean±S.D., if they were normally distributed. Differences in the normally distributed variables were assessed using the t test and the paired t test for dependent variables. Categorical variables were described with absolute and relative (percentage) frequencies. According to the above definition of contractile recovery, patients were classified into two groups: Group 1 with evidence of actual contractile improvement after revascularization at follow-up echocardiography and Group 2 with no such evidence of improvement. The two groups were compared with respect to patients’ clinical characteristics, and baseline echocardiographic and angiographic data, using the unpaired t test for continuous and the Pearson’s χ 2 test for categorical variables. Twenty cases were randomly selected for analysis of intraobserver variability. Assessment of variability was performed using linear regression analysis. A probability value of P <.05 was considered statistically significant. Analyses were performed with SPSS version 12.0 statistical package (SPSS, Chicago, IL, USA).
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
