Abstract
Background
Visualization of collateral circulation to the infarct-related artery on coronary angiography was suggested to predict viability in the infarct zone as demonstrated by dobutamine stress echocardiography.
Methods and materials
We enrolled 30 consecutive patients referred from our catheterization labs with prior Q-wave myocardial infarction at least 6 months before study enrollment. Patients were classified according to the presence of collaterals to the infarct-related artery into two groups: collateral group with Rentrop Grade 1–3 collaterals, and noncollateral group with Rentrop Grade 0 collaterals. Patients underwent resting 99m Tc-sestamibi imaging study with the administration of trimetazidine, using the standard technique, within 4 days of coronary angiography. Viability in a specific territory was defined when at least 50% of its individual segments were classified as viable.
Results
The visualization of collaterals by coronary angiography was able to predict viability in the territory supplied by the infarct-related artery with a sensitivity of 88.2%; specificity of 53.8%; positive and negative predictive values of 71.4% and 77.8%, respectively; and a diagnostic accuracy of 73.3%. The presence of viability increased progressively, in a statistically significant manner, from Rentrop Grade 0 to Grade 1 and Grade 2 [2 (22.2%), 5 (50%), 10 (91%), respectively, P =.04].
Conclusions
Visualization of coronary collaterals to the infarct-related artery by coronary angiography may predict with a high sensitivity but a low specificity the presence of viability in the territory supplied by that artery.
1
Introduction
With the vast progress in the field of coronary revascularization over the past two decades, predicting the presence of viable myocardium has acquired great clinical importance, especially in patients assigned for interventional treatment . Myocardial viability represents impairment in contractility that is potentially reversible if blood supply is adequately restored . Assumingly, improving blood flow to viable dysfunctional zones results in subsequent improvement of regional and global left ventricular function, heart failure symptoms, functional capacity, and long-term survival . This paradigm was supported by the results of several studies where only patients with severe left ventricular dysfunction who had viable myocardium improved after revascularization .
The visualization of collateral circulation to the infarct-related artery on coronary angiography was suggested to predict the presence of viability in the infarct zone as demonstrated by dobutamine stress echocardiography . In a retrospective study design, we sought to explore the ability of coronary collaterals to the infarct-related artery seen by coronary angiography to predict viability in the infarct territory as shown by 99m Tc-sestamibi single photon emission computed tomography (SPECT).
2
Patients and methods
2.1
Patient selection
The study included 30 consecutive patients referred to our catheterization labs with prior myocardial infarction, during the period from May 2004 to August 2005. Patients were considered eligible for inclusion if they had evidence of prior Q-wave myocardial infarction at least 6 months before study enrollment. Prior myocardial infarction was defined based on 12-lead electrocardiogram showing abnormal Q waves (≥1 mm in width) in at least two contiguous leads and previous laboratory evidence of elevated cardiac biomarkers at the time of the index infarction: CK-MB and/or troponin more than twice the upper limit of normal laboratory reference. The indication for coronary angiography was postinfarction angina in all patients. We excluded patients with prior non-Q-wave myocardial infarction; those with postinfarction severe hemodynamic instability; those with significant valvular or congenital heart disease, or any myocardial disease apart from ischemia; those who underwent prior percutaneous coronary angioplasty or surgical coronary bypass; those with atrial fibrillation or bundle branch block; those with marked obesity (body mass index >30); and those with limited life expectancy due to coexistent disease (e.g., malignancy). Patients were receiving conventional medical therapy according to standard clinical practice. Before inclusion, an informed written 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, as revised in 2002.
2.2
Definitions
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. Heart failure was defined clinically according to the standard criteria as validated by the Framingham Heart Study . Diagnosis required the simultaneous presence of at least two major criteria or one major criterion in conjunction with two minor criteria. Major criteria included paroxysmal nocturnal dyspnea, neck vein distension, rales, radiographic cardiomegaly, acute pulmonary edema, S 3 gallop, increased central venous pressure (>16 cmH 2 O at right atrium), hepatojugular reflux, and weight loss >4.5 kg in 5 days in response to treatment. Minor criteria included bilateral ankle edema, nocturnal cough, dyspnea on ordinary exertion, hepatomegaly, pleural effusion, decrease in vital capacity by one third from maximum recorded, and tachycardia (heart rate >120 beats/min).
2.3
Coronary angiography
All patients underwent selective left and right coronary arteriography using the standard technique, and the angiographic data were retrospectively analyzed by a single expert independent interventionalist, blinded to the clinical findings. No intracoronary pharmacologic agents were given. Each major epicardial vessel was assessed in at least two perpendicular planes, and the infarct-related artery (predicted from the site of myocardial infarction seen in electrocardiogram) was identified by either total occlusion or evidence of plaque ulceration. Collateral circulation to the infarct-related artery was evaluated according to the classification system described by Rentrop et al. (Grade 0=no visible coronary collaterals. Grade 1=collateral circulation fills only the side branches of the recipient coronary artery. Grade 2=collateral circulation partially fills the epicardial segments of the recipient coronary artery. Grade 3=collateral circulation completely fills the epicardial segments of the recipient coronary artery). Patients were classified into two groups: collateral group with Rentrop Grade 1–3 collaterals and noncollateral group with Rentrop Grade 0 collaterals. Retrospective data were extracted by reviewing the angiographic data registered in the database of our catheterization laboratory.
2.4
99m Tc-Sestamibi SPECT imaging protocol
Patients underwent resting 99m Tc-sestamibi imaging study with the administration of trimetazidine, using the standard imaging technique, within 4 days of coronary angiography, provided that no ischemic events were recorded during the time from coronary angiography to 99m Tc-sestamibi imaging. Trimetazidine [trimetazidine dihydrochloride (Vastarel), Servier, France] was administered by the oral route the day before the study (60 mg in three divided equal doses 8 h apart) and 1 h before performing the study (60 mg single dose). Injection of 25–30 mCi of radioactive tracer was performed 45–60 min before SPECT image acquisition. Images were acquired using a rotating single-head gamma camera (GE Starcam 4000i, UK) equipped with low-energy all-purpose collimators. Energy windows of 20% were respectively centered on the 140-keV peaks of 99m Tc-sestamibi. Thirty-two images were obtained over 180° extending from the 45° right anterior oblique to the 45° left posterior oblique projections. All studies were subjected to quality- control checks and corrections when necessary for camera nonuniformity, center-of-rotation offsets, patient motion, and “upward creep” .
2.5
99m Tc-Sestamibi SPECT image analysis
Two experienced nuclear cardiologists blinded to the clinical and angiographic data analyzed the SPECT images. The vascular assignment of myocardial segments to the conventional anatomic distribution of major coronary arteries was performed according to the 17-segment scoring system . Segmental 99m Tc-sestamibi uptake was scored by use of the four-point scoring system. Patterns of viability were based on the segmental radiotracer uptake . Segments were then individually classified into viable or nonviable. The presence of viability in a specific coronary arterial territory was defined when at least 50% of its individual segments were classified as viable .
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. Categorical variables were described with absolute and relative (percentage) frequencies. For testing the hypothesis of no difference between groups, a Fisher’s Exact Test or χ 2 test was used for categorical variables, as appropriate. The sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy were calculated according to the standard definitions. The distribution of myocardial viability among the different Rentrop grades of coronary collateral development, and the correlation between heart failure and viability were compared using the Pearson χ 2 test. All tests were two sided and a probability value of P <.05 was considered statistically significant. Analyses were performed with the SPSS version 12.0 statistical package (SPSS, Inc., Chicago, IL, USA).
2
Patients and methods
2.1
Patient selection
The study included 30 consecutive patients referred to our catheterization labs with prior myocardial infarction, during the period from May 2004 to August 2005. Patients were considered eligible for inclusion if they had evidence of prior Q-wave myocardial infarction at least 6 months before study enrollment. Prior myocardial infarction was defined based on 12-lead electrocardiogram showing abnormal Q waves (≥1 mm in width) in at least two contiguous leads and previous laboratory evidence of elevated cardiac biomarkers at the time of the index infarction: CK-MB and/or troponin more than twice the upper limit of normal laboratory reference. The indication for coronary angiography was postinfarction angina in all patients. We excluded patients with prior non-Q-wave myocardial infarction; those with postinfarction severe hemodynamic instability; those with significant valvular or congenital heart disease, or any myocardial disease apart from ischemia; those who underwent prior percutaneous coronary angioplasty or surgical coronary bypass; those with atrial fibrillation or bundle branch block; those with marked obesity (body mass index >30); and those with limited life expectancy due to coexistent disease (e.g., malignancy). Patients were receiving conventional medical therapy according to standard clinical practice. Before inclusion, an informed written 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, as revised in 2002.
2.2
Definitions
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. Heart failure was defined clinically according to the standard criteria as validated by the Framingham Heart Study . Diagnosis required the simultaneous presence of at least two major criteria or one major criterion in conjunction with two minor criteria. Major criteria included paroxysmal nocturnal dyspnea, neck vein distension, rales, radiographic cardiomegaly, acute pulmonary edema, S 3 gallop, increased central venous pressure (>16 cmH 2 O at right atrium), hepatojugular reflux, and weight loss >4.5 kg in 5 days in response to treatment. Minor criteria included bilateral ankle edema, nocturnal cough, dyspnea on ordinary exertion, hepatomegaly, pleural effusion, decrease in vital capacity by one third from maximum recorded, and tachycardia (heart rate >120 beats/min).
2.3
Coronary angiography
All patients underwent selective left and right coronary arteriography using the standard technique, and the angiographic data were retrospectively analyzed by a single expert independent interventionalist, blinded to the clinical findings. No intracoronary pharmacologic agents were given. Each major epicardial vessel was assessed in at least two perpendicular planes, and the infarct-related artery (predicted from the site of myocardial infarction seen in electrocardiogram) was identified by either total occlusion or evidence of plaque ulceration. Collateral circulation to the infarct-related artery was evaluated according to the classification system described by Rentrop et al. (Grade 0=no visible coronary collaterals. Grade 1=collateral circulation fills only the side branches of the recipient coronary artery. Grade 2=collateral circulation partially fills the epicardial segments of the recipient coronary artery. Grade 3=collateral circulation completely fills the epicardial segments of the recipient coronary artery). Patients were classified into two groups: collateral group with Rentrop Grade 1–3 collaterals and noncollateral group with Rentrop Grade 0 collaterals. Retrospective data were extracted by reviewing the angiographic data registered in the database of our catheterization laboratory.
2.4
99m Tc-Sestamibi SPECT imaging protocol
Patients underwent resting 99m Tc-sestamibi imaging study with the administration of trimetazidine, using the standard imaging technique, within 4 days of coronary angiography, provided that no ischemic events were recorded during the time from coronary angiography to 99m Tc-sestamibi imaging. Trimetazidine [trimetazidine dihydrochloride (Vastarel), Servier, France] was administered by the oral route the day before the study (60 mg in three divided equal doses 8 h apart) and 1 h before performing the study (60 mg single dose). Injection of 25–30 mCi of radioactive tracer was performed 45–60 min before SPECT image acquisition. Images were acquired using a rotating single-head gamma camera (GE Starcam 4000i, UK) equipped with low-energy all-purpose collimators. Energy windows of 20% were respectively centered on the 140-keV peaks of 99m Tc-sestamibi. Thirty-two images were obtained over 180° extending from the 45° right anterior oblique to the 45° left posterior oblique projections. All studies were subjected to quality- control checks and corrections when necessary for camera nonuniformity, center-of-rotation offsets, patient motion, and “upward creep” .
2.5
99m Tc-Sestamibi SPECT image analysis
Two experienced nuclear cardiologists blinded to the clinical and angiographic data analyzed the SPECT images. The vascular assignment of myocardial segments to the conventional anatomic distribution of major coronary arteries was performed according to the 17-segment scoring system . Segmental 99m Tc-sestamibi uptake was scored by use of the four-point scoring system. Patterns of viability were based on the segmental radiotracer uptake . Segments were then individually classified into viable or nonviable. The presence of viability in a specific coronary arterial territory was defined when at least 50% of its individual segments were classified as viable .
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. Categorical variables were described with absolute and relative (percentage) frequencies. For testing the hypothesis of no difference between groups, a Fisher’s Exact Test or χ 2 test was used for categorical variables, as appropriate. The sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy were calculated according to the standard definitions. The distribution of myocardial viability among the different Rentrop grades of coronary collateral development, and the correlation between heart failure and viability were compared using the Pearson χ 2 test. All tests were two sided and a probability value of P <.05 was considered statistically significant. Analyses were performed with the SPSS version 12.0 statistical package (SPSS, Inc., Chicago, IL, USA).
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
