CLINICAL STUDY: INTERVENTIONAL CARDIOLOGY
TIMI frame count immediately after primary coronary angioplasty as a predictor of functional recovery in patients with TIMI 3 reperfused acute myocardial infarction
Shinichi Hamada, MD*,
Takashi Nishiue, MD*,
Seishi Nakamura, MD*,
Tetsuro Sugiura, MD ,
Hiroshi Kamihata, MD*,
Hironori Miyoshi, MD*,
Yusuke Imuro, MD* and
Toshiji Iwasaka, MD*
* Cardiovascular Center, Kansai Medical University, Osaka, Japan
Department of Clinical Laboratory Medicine, Kochi Medical School, Kochi, Japan
Manuscript received December 6, 2000;
revised manuscript received April 25, 2001,
accepted May 17, 2001.
Reprint requests and correspondence: Dr. Shinichi Hamada, Cardiovascular Center, Kansai Medical University, 10-15 Fumizono-cho, Moriguchi, Osaka, 570-8507, Japan
shamada{at}remus.dti.ne.jp
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Abstract
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OBJECTIVES
The purpose of this study was to evaluate whether higher coronary blood flow, estimated by the corrected Thrombolysis In Myocardial Infarction (TIMI) frame count (CTFC), is related to better functional and clinical outcome after successful percutaneous transluminal coronary angioplasty (PTCA) in patients with acute myocardial infarction (AMI).
BACKGROUND
Experimental studies have found that functional recovery of the infarcted myocardium was associated with increased blood flow (reactive hyperemia) to the infarcted bed shortly after reperfusion.
METHODS
We measured CTFC immediately after successful (TIMI 3) primary PTCA in 104 consecutive patients with their first AMI. Wall motion score index (WMSI) and the presence of pericardial effusion were assessed by two-dimensional echocardiography before and one month after PTCA.
RESULTS
The patients were divided into two groups according to mean CTFC for corresponding coronary artery of the control group: TIMI 3 slow group (45 patients, 40 > CTFC  23) and TIMI 3 fast group (59 patients, CTFC < 23). There were no significant differences in the baseline characteristics and WMSI before reperfusion between the two groups. Improvement of WMSI in the TIMI 3 fast group was significantly greater than that of the TIMI 3 slow group (1.33 ± 0.52 vs. 0.60 ± 0.34, p < 0.001). Pericardial effusion and intractable heart failure were observed more frequently in the TIMI 3 slow group than in the TIMI 3 fast group (27 vs. 10%; p < 0.05, 36 vs. 17%; p < 0.05). Corrected TIMI frame count, assessed as a continuous variable, had a significant correlation with the change in WMSI (r = 0.60, p < 0.001) after adjusting for age, gender, history of hypertension, history of diabetes, elapsed time to PTCA, collateral grade, presence of antegrade flow before PTCA and number of diseased vessels.
CONCLUSIONS
Lower CTFC of the infarct-related artery immediately after PTCA was associated with greater functional recovery; and hence, CTFC can predict clinical and functional outcome in patients with successful PTCA.
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Abbreviations and Acronyms
| | AMI | = acute myocardial infarction | | CPK | = creatine phosphokinase | | CTFC | = corrected TIMI frame count | | ECG | = electrocardiogram | | IRA | = infarct-related artery | | LAD | = left anterior descending coronary artery | | LCX | = left circumflex coronary artery | | LV | = left ventricular, left ventricle | | PTCA | = percutaneous transluminal coronary angioplasty | | RCA | = right coronary artery | | TIMI | = Thrombolysis In Myocardial Infarction |  WMSI | = absolute change in the wall motion score index |
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The achievement of Thrombolysis In Myocardial Infarction (TIMI) 3 flow in the infarct-related artery (IRA) is the primary goal of reperfusion therapy in patients with acute myocardial infarction (AMI). Percutaneous transluminal coronary angioplasty (PTCA) has been widely performed because of better recanalization rate and less residual stenosis compared with thrombolytic therapy (1–4). However, myocardial tissue perfusion may remain impaired even after the achievement of TIMI 3 flow of the IRA without residual stenosis. The failure to achieve adequate tissue perfusion is referred to as the "no-reflow" or "low-reflow" phenomenon and is established at the time of reperfusion due to microcirculatory damage induced by ischemia (5–10).
The corrected TIMI frame count (CTFC) is a simple clinical tool for assessing quantitative indexes of coronary blood flow. This technique counts the number of cineangiographic frames from initial contrast opacification of the proximal coronary artery to opacification of distal arterial landmarks and is corrected for the length of left anterior descending coronary artery (LAD) (11,12). Although CTFC has been reported to be more accurate in predicting outcome of thrombolytic therapy after AMI (13), no study has examined the relationship between CTFC immediately after successful PTCA (TIMI 3) or clinical outcome in patients with AMI. Therefore, we evaluated CTFC after primary PTCA as a predictor of functional recovery and clinical outcome in patients with AMI.
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Methods
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Study population.
The study group consisted of 104 consecutive patients who were admitted to the coronary care unit of Kansai Medical University with their first AMI and who underwent revascularization within 12 h of onset by primary PTCA. Patients were selected on the following criteria: 1) <50% diameter stenosis with TIMI 3 flow of the IRA after primary PTCA; 2) no evidence of reinfarction during a one month follow-up period with enough good patency of the culprit lesion (IRA < 75% diameter stenosis) at follow-up angiography; and 3) adequate echocardiographic imaging quality. The diagnosis of AMI was based on chest pain lasting >30 min, persistent ST-segment elevation >0.1 mV in two or more contiguous leads on the 12-lead electrocardiogram (ECG) and increase in the serum creatine phosphokinase (CPK) levels with >5% MB fraction. The study protocol was approved by the Institutional Ethics Committee on Human Research, and informed consent was obtained from all patients.
Treatment regimen.
All patients were given aspirin (81 mg) and 3,000 U of intravenous heparin just after diagnosis of AMI. Two-dimensional echocardiographic images were obtained before reperfusion and at a mean of 27 days after the onset of AMI with a commercially available echocardiographic system equipped with a sector transducer (Sonos 2500, 5500 Agilent Technologies, Palo Alto, California). Parasternal long-axis, short-axis, apical two- and four-chamber views were recorded on S-VHS videotapes for later analysis. Primary PTCA was performed by conventional technique using the femoral approach. After arterial cannulation, all patients received heparin (7,000 IU) and isosorbide dinitrate (2 mg). After a 7F guiding catheter was positioned in the ostium of the coronary artery, baseline angiography was performed. Coronary flow of the IRA before and after PTCA was graded visually according to the TIMI Study group flow classification (14). Collateral flow before PTCA was graded visually using a classification by Rentrop et al. (15). Grade 0 collateral flow was defined as the absence of visible collaterals, grade 1 flow as the filling of side branches only, grade 2 flow as the filling of side branches and a portion of the main epicardial artery and grade 3 flow as complete filling of the side branches and epicardial vessel beyond the point of the occlusion. Adequate collateral was considered present when the collateral flow was graded 2 or 3. Subsequently, primary PTCA was performed using standard balloon dilation catheters, ranging in diameter from 2.0 mm to 4.0 mm, chosen according to the size of vascular regions adjacent to the stenosis. Angioplasty success was defined as <50% diameter stenosis with TIMI 3 flow (CTFC <40) of the IRA after primary PTCA. Adjunct stentings were performed in cases with 50% diameter stenosis. After achievement of TIMI 3 flow of IRA, coronary angiography was performed to measure CTFC after administration of isosorbide dinitrate (2 mg). Coronary angiography was repeated at one month after the onset of AMI to confirm the patency of IRA.
Echocardiographic data.
Echocardiographic images on admission (baseline) were used to assess the initial extent of left ventricular (LV) dysfunction. Follow-up image at one month after the onset of AMI was paired with the corresponding baseline image and directly compared to assess the change in regional wall motion. A semiquantitative scoring system was used to analyze each study. The LV was divided into 16 segments: short-axis slice at the levels of the mitral valve and midpapillary muscle divided into six segments. The apex of the LV was divided into four segments. Wall motion in each segment was evaluated as follows: 3, akinetic/dyskinetic; 2, severely hypokinetic; 1, hypokinetic; 0, normal. Wall motion score index (WMSI) was calculated as the mean score of the segments showing asynergy at baseline, and improvement of wall motion was calculated as the change in WMSI (WMSI before primary PTCA – one month). The presence of pericardial effusion was assessed at one month with the method described by Horowitz et al. (16). An epicardial-pericardial separation that persisted throughout the cardiac cycle (D pattern) was considered diagnostic of pericardial effusion (16). Wall motion score index and pericardial effusion were determined by two independent observers who had no knowledge of the clinical and angiographic data. In cases of disagreement, consensus was established with a third observer.
TIMI frame count.
Thrombolysis in Myocardial Infarction frame count was defined as the number of frames required for dye to first opacify a standard distal landmark. The TIMI frame of the coronary artery was obtained using the technique described by Gibson et al. (11). The TIMI frame count was measured with digital cardiac image sequence acquisitions (Advantx LC and DLX, GE Medical Systems, Chicago, Illinois) that were displayed and stored in a 512 matrix of simultaneously recorded images on the standard cine films. Live digital cardiac acquisitions can be closely compared to cineradiography. The important distinction between cine and live digital cardiac acquisitions is that digital cardiac acquisitions have an ability to perform optimal quantitative analysis measurements on live images (17). The frame rate of a digital cardiac image was calculated as 30 frames/s. The TIMI frame counts of 60 consecutive angiographically normal coronary arteries free of ischemic syndrome in our facility were obtained to determine the normal CTFC. The mean CTFC value obtained from these subjects was 23. Therefore, a cutoff point of 23 was used to divide TIMI fast versus slow. To correct the longer length of LAD from right coronary artery (RCA) or left circumflex coronary artery (LCX), the TIMI frame count of the LAD was divided by unadjusted TIMI frame count of the normal LAD, divided by the mean TIMI frame count of the RCA and LCX, yielding a CTFC. A CTFC was calculated by dividing the LADs’ TIMI frame counts by 1.7 to normalize for their longer lengths in accordance with standard methods (11). A CTFC of 40 has previously been identified as the cutpoint for distinguishing TIMI flow grade 3 versus 2 (11). By definition, all the patients in this study restored TIMI 3 flow of the culprit vessel after intervention (CTFC < 40). Assessment of CTFC and TIMI flow grade was made by two experienced observers blinded to other clinical data. Disagreement was resolved by a third observer. Intra-observer reproducibility was 2.9 ± 1.6 frames. Interobserver variability was 3.2 ± 1.75 frames.
Quantitative angiographic analysis.
Quantitative angiographic analysis was performed after angioplasty and at follow-up in matched views using an online system (QCA-QVA System, GE Medical System, Chicago, Illinois). Measurement was made with the use of a validated edge-detection algorithm. The following parameters were calculated as the mean values from two orthogonal views: reference diameter, minimal lumen diameter and percent diameter stenosis, respectively.
Definition of LV heart failure.
Left ventricular heart failure was defined as the presence of clinical congestive heart failure (the presence of a third heart sound, Killip class 2, Forrester subsets of 2 or 4, dyspnea or evidence of pulmonary congestion on chest radiographs).
Statistical analysis.
Results are expressed as mean ± SD. Comparisons between continuous variables were performed using Student t test or Mann-Whitney U test where applicable. Categorical variables were compared using Fisher exact probability test. Univariate linear regression analysis was used to assess the relation between CTFC and WMSI. Stepwise linear regression analysis (selection criterion p < 0.20) was performed to assess the important factors related to WMSI using nine clinical variables: age, gender, history of hypertension, history of diabetes, elapsed time to PTCA, collateral grade, presence of antegrade flow before PTCA, number of diseased vessels and CTFC. For all analysis, a p value <0.05 was considered significant.
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Results
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Baseline characteristics.
The mean TIMI frame counts of 60 angiographically normal coronary arteries were LAD: 38.6 ± 3.0, LCX: 23.6 ± 2.9 and RCA: 22.5 ± 3.1. The ratio of the TIMI frame count between LAD and RCA or LCX was 1.7, which was concordant with a previous report (11). The mean CTFC was 23 ± 3 in an angiographically normal coronary artery. Patients were divided into two groups according to mean CTFC of the corresponding coronary artery in the control group: 45 patients with 40 > CTFC 23 (TIMI 3 slow group) and 59 patients with CTFC < 23 (TIMI 3 fast group).
Baseline clinical characteristics are shown in Table 1. There were no significant differences between the two groups with regard to age, gender, peak CPK, LAD culprit location, collateral grade, incidence of coronary risk factors and single-vessel disease and TIMI flow grade before reperfusion. The blood pressure and heart rate were similar between the two groups. However, elapsed time from the onset of symptoms to reperfusion in the TIMI slow group was significantly longer than that of the TIMI fast group. Coronary stents were implanted in 12 patients in the TIMI slow group and in 17 patients in the TIMI fast group (p = 0.829).
Quantitative angiographic analysis.
The angiographic measurements immediately and one month after PTCA are summarized in Table 2. Although the diameter stenosis of the TIMI 3 slow group tended to be smaller than that of the TIMI fast group, reference vessel diameter and minimal lumen diameter were similar between the two groups immediately after PTCA. There were no significant differences between the two groups with regard to diameter stenosis, reference vessel diameter and minimal lumen diameter one month after PTCA.
Echocardiographic WMSI.
Figure 1 shows the change in WMSI from admission to one month. There was no significant difference in WMSI on admission between the two groups (TIMI 3 slow group; 2.91 ± 0.76 vs. TIMI 3 fast group; 2.82 ± 0.47, p = 0.48). The WMSI significantly improved at one month in both groups, but the WMSI in the TIMI 3 fast group was significantly larger than that of the TIMI 3 slow group (1.33 ± 0.52 vs. 0.60 ± 0.34, p < 0.001). Pericardial effusion and LV heart failure were observed more frequently in the TIMI 3 slow group than in the TIMI 3 fast group (Table 3).
Predictors of WMSI.
The relationship between WMSI and CTFC is presented in Figure 2. There was a significant negative correlation between WMSI and CTFC (r = –0.602, p < 0.001). When stepwise linear regression analysis was performed to evaluate the important factor, related WMSI, lower CTFC, shorter elapsed time and presence of antegrade flow before PTCA were the significant factors related to WMSI after adjustment for age, gender, history of diabetes, history of hypertension, collateral grade and number of diseased vessels (Table 4).
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Discussion
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The major finding of this study was that lower CTFC (faster coronary flow of IRA) in patients with TIMI 3 immediately after primary PTCA was associated with greater functional recovery and lower incidence of complications in the convalescent stage compared with those with higher CTFC. Moreover, lower CTFC immediately after primary PTCA was found to be the most powerful predictor for improvement of regional LV function by multivariate analysis.
Assessment of microvascular perfusion by intracoronary myocardial contrast echocardiography (7), positron emission tomography (8), radionuclide imaging (9) and Doppler guide wire (10) have revealed the no-reflow phenomenon in patients with TIMI 3 flow of the IRA. Because the no-reflow or low-reflow phenomenon was associated with poor functional recovery and adverse clinical events, many cardiologists have focused on microvascular reperfusion of infarcted myocardium as a final goal of reperfusion therapy. However, these modalities have not found widespread application for the assessment of microvascular perfusion, because of the demanding nature of the technique, high cost, time-consuming or not readily available in all coronary laboratories. Recently, CTFC has been proposed as a simple, inexpensive, reproducible and quantitative method to assess coronary blood flow (11). In this study, we measured CTFC from the digital angiographic recording system and found that CTFC can discriminate individual patients with poor functional recovery and adverse clinical events from those with favorable outcome in the catheterization laboratory at the time of reperfusion.
Previous studies.
Gibson et al. (13) reported that higher CTFC 90 min after thrombolytic therapy was related to increased risk of adverse outcome. Moreover, survivors of PTCA for acute coronary syndrome had lower CTFC than patients who died after PTCA (18). In this study, we clearly demonstrated that CTFC predicted the degree of functional recovery of the reperfused myocardium immediately after TIMI 3 reperfusion without residual coronary stenosis (percent diameter stenosis <50%). The CTFC may provide additional information about the degree of microcirculatory damage in patients with TIMI 3 reperfused AMI. Thus, CTFC at the time of reperfusion may enable identification of patients who would benefit from additional pharmacological adjunctive treatment, which attenuates microvascular dysfunction and augments myocardial blood flow in the reperfused myocardium, such as verapamil, nicorandil and adenosine (19–21). However, others were unable to demonstrate the relationship between CTFC and adverse clinical outcome or functional recovery after thrombolytic therapy (22,23). These previous studies included patients with TIMI 2 after a reperfusion procedure, which is regarded as reperfusion failure in AMI (24,25). Furthermore, two different types of phasic coronary flow are included in TIMI 2 flow: residual coronary stenosis and microvascular damage (26). Therefore, the discrepancy of these results may have been due to inclusion of TIMI 2 patients. Other explanations as to the reason for discrepancies in outcome may be based on methodological problems (27). Bhatt et al. (23) assessed flow to the distal circulation in addition to the CTFC landmark. If a more distal landmark was used, the variability in arterial length between patients would have affected CTFC, and a more distal landmark may incorporate an element of washout in the measurement (27).
Reactive hyperemic response to reperfusion.
Experimental studies have reported that flow to the risk area remains hyperemic or comparable to that in the nonischemic bed up to several hours after reperfusion (28–30). Heynderickx et al. (28) found that functional recovery of the infarcted myocardium was accompanied by marked increase in blood flow to the infarcted bed shortly after reperfusion. In a clinical setting, patients with CTFC <14 (TIMI flow grade 4) after thrombolysis or PTCA were reported to have excellent outcome (13). In this study, the degree of reactive hyperemic response after reperfusion assessed by CTFC predicted the degree of functional recovery of the reperfused myocardium; lack of reactive hyperemic response after reperfusion was associated with a delay in the recovery of LV function due to microvascular damages of the infarcted myocardium. Thus, not all TIMI flow grade 3 is created equally, even after successful primary PTCA; and CTFC may be used as a guide for the selection of newer revascularization strategies or pharmacological adjunctive treatment beyond TIMI flow grade 3 in patients with AMI.
Study limitations.
Several limitations of this study should be addressed. The CTFC is affected by residual coronary stenosis, but none of our patients had significant residual stenosis in the IRA as assessed by quantitative angiographic analysis after PTCA. Although we did not confirm the lumen cross-sectional area by intravascular ultrasound, there may be a limitation of lumen enlargement despite satisfactory lumen enlargement by the angiogram (31). Second, cardiac enzyme was not evaluated to estimate the infarct size. In addition to methodological problems and small sample size, the course of cardiac enzyme release may also be interfered with by hyperemic response, which makes the enzymatic assessment difficult to estimate the infarct size. Third, ST-segment resolution on ECG 1 h after the reperfusion is also known as a simple prognostic parameter after reperfused AMI (22,32). Although we did not make any comparison between ST-segment resolution on ECG and CTFC as a prognostic parameter, CTFC at the time of reperfusion can be used as a predictor in the earlier phase of AMI. Finally, we regarded the TIMI fast flow as a reactive hyperemia. Several factors have been reported as determinants of the reperfused coronary flow velocity, including viscosity of blood (33,34), preload, afterload (35) and the extent of the reperfusion injury (5). Since we made no attempt to measure blood viscosity and the LV end-diastolic pressure at the time of reperfusion, CTFC in our results cannot be directly applied to the absolute microvascular flow to the infarcted myocardium. However, our findings have relevance to the net results of coronary flow to the infarcted myocardium, including these factors. Further CTFC studies are required for a more complete understanding of the physiologic impact of these factors on coronary circulation in patients with reperfused myocardial infarction.
Conclusions.
The CTFC may be used to identify the high-risk group after AMI at the time of reperfusion in patients with AMI beyond TIMI flow grade 3. Absence of reactive hyperemic response after reperfusion, high CTFC, was associated with poor functional recovery and outcome.
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G. Beran, I. Lang, W. Schreiber, S. Denk, T. Stefenelli, B. Syeda, G. Maurer, D. Glogar, and P. Siostrzonek
Intracoronary Thrombectomy With the X-Sizer Catheter System Improves Epicardial Flow and Accelerates ST-Segment Resolution in Patients With Acute Coronary Syndrome: A Prospective, Randomized, Controlled Study
Circulation,
May 21, 2002;
105(20):
2355 - 2360.
[Abstract]
[Full Text]
[PDF]
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Abstract
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