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J Am Coll Cardiol, 2004; 43:534-541, doi:10.1016/j.jacc.2003.08.055 © 2004 by the American College of Cardiology Foundation |
* Department of Cardiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
Manuscript received June 16, 2003; revised manuscript received July 23, 2003, accepted August 5, 2003.
* Reprint requests and correspondence: Dr. Jan J. Piek, Department of Cardiology B2-125, Academic Medical Center, P.O. Box 22700, 1100 DE Amsterdam, The Netherlands.
j.j.piek{at}amc.uva.nl
| Abstract |
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BACKGROUND: Angiographic, intracoronary Doppler flow, and electrocardiographic variables have been reported to be predictors of recovery of LV function after acute myocardial infarction (MI). We directly compared the predictive value of Thrombolysis In Myocardial Infarction (TIMI) flow grade, corrected TIMI frame count (cTfc), myocardial blush grade, coronary Doppler flow velocity analysis, and resolution of ST-segment elevation for recovery of LV function in patients undergoing primary PCI for acute MI.
METHODS: We prospectively studied 73 patients who underwent PCI for an acute anterior MI. Recovery of global and regional LV function was measured using an echocardiographic 16-segment wall motion index (WMI) before PCI, at 24 h, at one week, and at six months. Directly after successful PCI, coronary flow velocity reserve (CFR), cTfc, TIMI flow grade, and myocardial blush grade were assessed.
RESULTS: Mean global and regional WMI improved gradually over time from 1.86 ± 0.23 before PCI to 1.54 ± 0.34 at six-month follow-up (p < 0.0001) and from 2.39 ± 0.30 before PCI to 1.87 ± 0.48 at six-month follow-up (p < 0.0001), respectively. Multivariate analysis revealed CFR as the only independent predictor for global and regional recovery of LV function at six months.
CONCLUSIONS: Doppler-derived CFR is a better prognostic marker for LV function recovery after anterior MI than other currently used parameters of myocardial reperfusion.
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The purpose of this study was to identify early determinants (at the time of reperfusion) of recovery of LV function by a direct comparison of the aforementioned parameters in patients with acute MI treated with primary percutaneous coronary intervention (PCI).
| Methods |
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Primary angioplasty and Doppler flow measurements. Primary PCI was performed within 6 h after the onset of symptoms via 6F sheath in the femoral artery, according to standard clinical practice with provisional stent implantation. Coronary angiography was performed at the end of PCI for off-line flow analyses. Five to 10 min after successful PCI, blood flow velocity was measured with a 0.014 inch Doppler wire (FloWire, Jomed, Ulestraten, The Netherlands) distal to the lesion. Coronary flow velocity reserve was determined as the ratio of adenosine (20 µg intracoronary), induced hyperemic average peak flow velocity (APV), and baseline APV. Flow velocities were recorded continuously on videotape (FloMap, Jomed). Coronary flow velocity reserve was also measured in an angiographically normal (diameter stenosis <30%) reference artery at the end of the procedure. A 12-lead ECG was performed before and at the end of PCI to evaluate ST-segment deviation.
Concomitant medical therapy. All patients were treated with aspirin 300 mg orally and heparin 5,000 IU intravenously before the procedure. An additional 2,500 IU heparin intravenously was administered if the procedure lasted more than 90 min. According to the protocol, patients subsequently received unfractionated heparin for 48 h, aspirin 100 mg daily, and ticlopidine 250 mg or clopidogrel 75 mg once daily after stent placement. Captopril was administered within 24 h after PCI and uptitrated if possible to 25 mg three times a day, metoprolol 50 mg twice a day, uptitrated if possible. Statin treatment was started the day after admission irrespective of serum cholesterol values.
LV function evaluation and follow-up. Two-dimensional echocardiography was performed immediately before primary PCI with a commercially available imaging system (Philips SONOS 2500, 2.0/2.5 MHz transducer). Data was stored on videotape. Echocardiographic evaluation of the LV function was repeated at day one, at one week, and at six months follow-up. After five weeks, a gated radionuclide ventriculography was performed. At six months follow-up, coronary angiography was repeated to assess vessel patency and/or restenosis. At six months, all patients were evaluated for major events, defined as death from all causes, non-fatal reinfarction, repeat PCI, or coronary artery bypass grafting.
Data extraction. The sum of ST-segment elevations was measured manually 80 ms after the end of the QRS complex (J-point) in leads I, aVL, and V1 through V6. Resolution of ST-segment elevation was expressed as a percentage of the initial ST-segment elevation. Resolution of >70% was defined as indicative for good myocardial reperfusion (14).
Collateral flow to the IRA was graded before PCI, according to Rentrop's classification (15). The TIMI flow and myocardial blush were graded (7,10), and cTfc was measured (9) off-line. The ratepressure product was defined as the product of heart rate and systolic blood pressure at the end of the procedure. Doppler flow velocity spectra were analyzed off-line to determine the following parameters: diastolic APV, diastolic deceleration time with a cutoff value of 600 ms (11), average antegrade systolic flow velocity with a cutoff value of 6.5 cm/s (11), the calculated ratio of mean diastolic-to-systolic flow velocity and early systolic retrograde flow velocity defined as retrograde peak velocity
10 cm/s, and duration
60 ms as previously described (16).
A 16-segment model was used to determine systolic LV function (17). All segments with a good delineation of the endocardium were scored: 1 = normal, 2 = hypokinesis, 3 = akinesis, 4 = dyskinesis. Global wall motion score index (WMI) was calculated by summation of the scores divided by the number of analyzed segments. Nine segments were used to calculate regional WMI: basal and mid-anteroseptal; mid-septal; apico-septal; apico-lateral; basal-, mid-, and apico-anterior; and apico-inferiorusually representing the perfusion territory of the left anterior descending [LAD] artery.
Recovery of global and regional LV function was defined as the difference in global and, respectively, regional WMI before PCI and that at specific time points at follow-up.
Statistical analysis. The study cohort consisted of patients who had an uneventful follow-up with an analyzable six-month follow-up echocardiography. The primary end point was recovery of LV function at six months, as defined above. Variables are presented as percentage of number of patients. Continuous variables are expressed as mean ± SD. Normally distributed variables were tested by two-tailed Student t test for paired or unpaired data, as appropriate, or by one-way analysis of variance (ANOVA) for more than two independent groups of data. The categorical variables were compared by chi-square or Fisher exact test where appropriate. Changes in global and regional WMI were tested by ANOVA for repeated measures. A p value <0.05 was considered statistically significant. Regression lines were obtained by least squares regression method. After determining univariate predictors of recovery of LV function and ejection fraction, multivariate stepwise linear regression analysis was applied to univariate variables with a significance level lower than 0.15. Qualitative variables were coded as 1 when the property was present and as 0 when absent. Statistical analysis was performed with SPSS version 10.0.7 (SPSS Inc., Chicago, Illinois).
| Results |
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Baseline characteristics. Baseline clinical characteristics are shown in Table 1. Angiographic, Doppler, and procedural characteristics are shown in Table 2. Mean age of the analyzed patients was 54 ± 12 years. Mean summated ST-segment elevation before PCI was 26.5 ± 14.8 mV and after the procedure 7.9 ± 6.1 mV resulting in 18.6 ± 12.2 mV absolute ST-segment resolution. The relative resolution was 70.2 ± 23.0%. Mean time between reperfusion and second ECG was 106 ± 30 min.
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At the end of the PCI procedure, mean CFR in the LAD coronary artery was 1.62 ± 0.37 (range, 1.0 to 2.6), with a mean baseline APV of 20.1 ± 8.5 cm/s and a mean hyperemic APV of 32.0 ± 14.1 cm/s. The mean reference vessel CFR was 2.43 ± 0.53. In the LAD coronary artery, mean diastolic decleration time was 635 ± 382 ms, mean average systolic flow velocity 9.9 ± 8.4 cm/s, mean diastolic-to-systolic flow velocity 4.2 ± 6.2, and mean early systolic retrograde flow velocity 6.3 ± 11 cm/s. Baseline APV in the LAD coronary artery showed fair correlations with TIMI flow grade (r = 0.31, p = 0.007) and cTfc (r = 0.54, p < 0.0001). No association was found between baseline APV and myocardial blush grade. A fair correlation existed between baseline APV and ST-segment resolution (r = 0.40, p = 0.003). Hyperemic APV in the LAD coronary artery was associated with TIMI flow grade (r = 0.35, p = 0.003), cTfc (r = 0.50, p < 0.0001), myocardial blush grade (r = 0.25, p = 0.04), and with ST-segment resolution (r = 0.29, p = 0.04). There was no significant correlation between CFR and any of the angiographic parameters or between CFR and ST-segment resolution. Mean peak CK-MB was 486 ± 255 µg/l.
Recovery of global and regional LV function. A progressive improvement of short-term and long-term global and regional LV function was documented (Table 3). All baseline variables were used to identify univariate predictors for short-term and long-term global (data not shown) and regional (Tables 1 and 2) LV function recovery.
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2.0 immediately after primary PCI showed improvement of LV function (Fig. 1A). No relation existed between angiographic parameters and recovery of LV function (Fig. 1B, 1C, and 1D).
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| Discussion |
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ST-segment resolution and LV function recovery. In contrast with earlier studies (14,18,19), we could not demonstrate a relation between ST-segment recovery and ejection fraction nor between ST-segment recovery and improvement of LV function. Our results are in accordance with the results of Poli et al. (19) as they found, with respect to six-month functional recovery, no additional prediction of ST-segment resolution next to myocardial blush grade. ST-segment resolution is proposed as a marker of microvascular reperfusion (20). However, in our study, no relation existed between ST-segment resolution and CFR, although it was associated with baseline and hyperemic APV. In previous studies, ST-segment resolution was slower in patients with anterior MI than with non-anterior MI. This may explain the absence of association between ST resolution and CFR in our study in patients with only anterior MI.
Angiographic parameters in relation to LV function recovery. Our current knowledge on factors influencing LV function recovery after acute MI is based on angiographic studies. In large, multicenter studies evaluating thrombolysis, TIMI flow grading appeared to be of clinical use for risk stratification (2,8,21). In our study, TIMI flow after PCI showed a weak correlation with LV function recovery at one week (r = 0.30, p = 0.015), and myocardial blush grade was weakly correlated with regional function recovery at one day (r = 0.27, p = 0.02). Our study consisted of non-high-risk patients (excluding shock, low ejection fraction, previous anterior MI, and excluding cardiac events on follow-up). This may be the reason for a diminished ability to detect a relationship between angiographic parameters and LV function recovery, whereas CFR is a potent predictor of LV function recovery in these patients.
Doppler-flow parameters in relation to LV function recovery. In our study, CFR was the only independent predictor of long-term global and regional LV function recovery. Coronary flow velocity reserve after PCI predicted not only the change in LV function over six months but also the ventriculographic ejection fraction at five weeks that is associated with long-term mortality. Coronary flow velocity reserve as a predictor being superior to the other parameters of myocardial perfusion may be explained by the direct way of interrogating the microvascular bed, thereby more accurately reflecting microvascular integrity and function.
Iwakura et al. (16) demonstrated altered coronary flow velocity patterns as the appearance of systolic retrograde flow, diminished systolic antegrade flow, and rapid deceleration of diastolic flow in patients with the no-reflow phenomenon after reperfusion therapy. These flow velocity patterns appeared to be inversely related with in-hospital (22) and with one-month recovery of LV function (11). This is in accordance with our findings that absence of early systolic retrograde flow immediately after primary PCI was associated with recovery of global and regional LV function at one-day follow-up and with regional LV function improvement at one week. At five weeks, systolic retrograde flow, next to CFR, independently correlated with ejection fraction. However, long-term LV function changes were not predicted by altered coronary flow velocity patterns in contrast with CFR. Surprisingly, CFR was not assessed in the aforementioned studies. Although altered flow patterns after primary PCI could predict in-hospital complications and mortality (23), it is unclear if these flow patterns can predict also long-term mortality.
Study limitations. This study was designed to evaluate prognostic parameters obtained during primary PCI on LV function recovery. The present study indicates that CFR is a good prognostic parameter for LV function recovery, although larger studies are needed for evaluation of Doppler-derived parameters to predict mortality.
In this study we did not perform intracoronary pressure measurements with microvascular resistance calculations. Combined and repeated coronary flow and pressure assessment in the early and late phase of MI may give more insight into changes in microvascular resistance in relation to LV function recovery.
Clinical implications. Our study suggests that CFR immediately after primary PCI can predict LV function recovery. This finding is relevant for selection of patients that may benefit from adjunctive therapies aiming at improving tissue reperfusion and, hence, recovery of LV function.
Conclusions. Percutaneous coronary intervention in patients with acute MI reduces infarct size and preserves LV function. Preservation of the microvascular function, and thus, of the integrity of myocardial tissue, is the pivotal factor influencing recovery of LV function after primary PCI. This study demonstrates that Doppler-derived CFR better predicts recovery of LV function than the commonly reported angiographic and clinical parameters.
| Acknowledgments |
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| References |
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