Abstract
Background
Successful recanalization of true chronic total occlusion (CTO) has been linked to a decrease in cardiac mortality. We evaluated the effect of CTO recanalization on LVEF and regional wall motion using paired cardiac magnetic resonance imaging (cMRI) studies.
Methods and results
43 patients underwent contrast enhanced cMRI prior to and 9 months after successful recanalization of a true CTO defined as thrombolysis in myocardial infarction flow 0 and duration of occlusion of more than 3 months. Regional wall motion was analyzed using the AHA model. For each segment the wall thickness (WT) was measured over the duration of one heart cycle and segmental wall thickening (SWT) was calculated. Left ventricular ejection fraction (LVEF) and volumes were measured. LVEF significantly increased by 2.4 ± 6.0% (p = 0.01). The increase was confined to patients with baseline LVEF below the median of 49.3% (4.1 ± 7.0%, p = 0.01) compared to 0.6 ± 4.0 (p = 0.48) in patients with baseline LVEF higher than the median. Segmental wall motion analysis was performed in 706 myocardial segments. SWT significantly increased in segments within the perfusion territory of the CTO vessel (5.1 ± 30.4%, p = 0.01), especially in dysfunctional segments at baseline with SWT init < 45% (13.3 ± 24.3%, p < 0.001). In addition, SWT significantly increased in segments of non-CTO vessels (4.1 ± 32.1%, p < 0.01).
Conclusions
In conclusion, in patients with successful recanalization of CTO left ventricular ejection fraction and regional wall motion are significantly improved, especially in patients with decreased LVEF and in dysfunctional segments.
Highlights
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LV-EF significantly improves after recanalization of true CTO.
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LV-EF improvement is more pronounced in patients with reduced baseline LV-EF.
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Segmental wall thickening (SWT) significantly increased in CTO segments.
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SWT improvement is more pronounced in dysfunctional CTO segments at baseline.
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SWT significantly increased in segments of non-CTO vessels.
1
Introduction
Among patients with coronary artery disease who underwent coronary angiography, prevalence of at least one coronary total occlusion (CTO) lesion was is up to 35% .
Successful percutaneous coronary intervention (PCI) of occluded lesions leads to complete revascularization and has been associated with lower mortality as well as an increase in LV function . Contrast enhanced cardiac magnetic resonance imaging (cMRI) has been shown to be a powerful tool to assess and predict myocardial perfusion, viability and function before and after PCI . With increasing success rates and growing numbers of CTO-PCI performed, outcome on left ventricular functional parameters and wall-motion with cMRI is scarce, especially regarding strictly defined true CTO lesions . MR image quality allows for accurate quantitative wall-motion analysis in single segments .
We used cMRI to evaluate the benefit of successful true CTO recanalization regarding improvement of regional as well as global left ventricular function.
2
Methods
We enrolled 43 patients who underwent successful recanalization of a true CTO and cMRI pre recanalization and 9 months after the intervention (Coronary and Structural Interventions Ulm — Coronary Chronic Total Occlusions; CSI-Ulm-CTO, NCT02162082). Indications for recanalization were symptoms and/or presence of vital myocardium within the perfusion territory of the occluded vessel. The study was approved by the ethics committee and patients gave written informed consent. True CTO lesions were defined as lesions with thrombolysis in myocardial infarction (TIMI) flow 0 and duration of occlusion greater than 3 months. Recanalization was performed via antegrade or retrograde approach, using bilateral coronary angiography. Implantation of drug-eluting stents was performed with predilatation and high-pressure post dilation. Procedural success was defined as TIMI flow 3 with residual diameter stenosis of less than 20%.
2.1
Magnetic resonance imaging
Patients underwent cMRI study prior to and 9 months after successful recanalization. CMRI was conducted using a 1.5-T scanner with peak intensity of 30 mT/min and a slew rate of 150 mT/m per second (Intera CV, Philips Medical Systems, Best, The Netherlands) in combination with a 5-element phased-array cardiac coil. Cardiac gating and breath holding techniques were employed. Image acquisition was realized using cine-imaging in combination with an ECG-triggered Steady-State-Free-Precision (SSFP) sequence. Acquisition parameters used were TE 1.7 ms, TR 3.4 ms and SENSE factor 2. Voxel size depended on the required field of view, ranging from 1.7 × 1.8 mm to 2.3 × 1.8 mm. Slice thickness was 10 mm without discontinuity . Delayed enhancement imaging was performed 15 min after injection of 0.2 mmol/l Gadolinium-DTPA (Magnevist, Schering, Berlin). A T1 3D inversion-recovery turbo gradient echo (TGE) sequence was used for image acquisition. The optimal 180° prepulse delay for signal suppression of the myocardium was determined for every patient individually using a Look–Locker sequence . Slice thickness for late enhancement (LE) imaging was 5–10 mm, depending on the required field of view.
2.2
Image analysis
Image analysis was performed on a specialized cMRI workstation running “View Forum” and, for the wall-motion analysis, “Cardiac Explorer” (both Philips Medical Systems, Best, The Netherlands). LV function and volumes were quantified using the Simpson rule. Segmental analysis was performed by using a modified AHA 17-segment model, excluding the apex . In the short axis views endocardial and epicardial contours were drawn into representative planes and traced. Segmental wall thickening (SWT) was calculated for every segment by the following formula:
S W T = max . wall thickness – min . wall thickness / max . wall thickness * 100 %
Segments were classified as dysfunctional when initial SWT was < 45%. Quantification of late-enhancement images was performed by automatic selection of voxels with enhancement greater than 2 standard deviations from a sample area of vital myocardium. Segments were scored according to the percentage of enhanced myocardium using the transmural extent of infarction scale (TEI) ranging from I to V. TEI-I was defined as 0%, TEI-II as < 25%, TEI-III as 25–50%, TEI-IV as 50–75% and TEI-V as 75–100% enhanced segmental volume .
2.3
Statistical analysis
All values are presented as counts (N) and percentages or as mean ± one standard deviation (SD). Discrete variables were analyzed using Fisher’s exact and Chi-Squared tests. Continuous variables were analyzed with Students t-test or one-way analysis of variance (ANOVA). A p-value < 0.05 was regarded as statistically significant.
2
Methods
We enrolled 43 patients who underwent successful recanalization of a true CTO and cMRI pre recanalization and 9 months after the intervention (Coronary and Structural Interventions Ulm — Coronary Chronic Total Occlusions; CSI-Ulm-CTO, NCT02162082). Indications for recanalization were symptoms and/or presence of vital myocardium within the perfusion territory of the occluded vessel. The study was approved by the ethics committee and patients gave written informed consent. True CTO lesions were defined as lesions with thrombolysis in myocardial infarction (TIMI) flow 0 and duration of occlusion greater than 3 months. Recanalization was performed via antegrade or retrograde approach, using bilateral coronary angiography. Implantation of drug-eluting stents was performed with predilatation and high-pressure post dilation. Procedural success was defined as TIMI flow 3 with residual diameter stenosis of less than 20%.
2.1
Magnetic resonance imaging
Patients underwent cMRI study prior to and 9 months after successful recanalization. CMRI was conducted using a 1.5-T scanner with peak intensity of 30 mT/min and a slew rate of 150 mT/m per second (Intera CV, Philips Medical Systems, Best, The Netherlands) in combination with a 5-element phased-array cardiac coil. Cardiac gating and breath holding techniques were employed. Image acquisition was realized using cine-imaging in combination with an ECG-triggered Steady-State-Free-Precision (SSFP) sequence. Acquisition parameters used were TE 1.7 ms, TR 3.4 ms and SENSE factor 2. Voxel size depended on the required field of view, ranging from 1.7 × 1.8 mm to 2.3 × 1.8 mm. Slice thickness was 10 mm without discontinuity . Delayed enhancement imaging was performed 15 min after injection of 0.2 mmol/l Gadolinium-DTPA (Magnevist, Schering, Berlin). A T1 3D inversion-recovery turbo gradient echo (TGE) sequence was used for image acquisition. The optimal 180° prepulse delay for signal suppression of the myocardium was determined for every patient individually using a Look–Locker sequence . Slice thickness for late enhancement (LE) imaging was 5–10 mm, depending on the required field of view.
2.2
Image analysis
Image analysis was performed on a specialized cMRI workstation running “View Forum” and, for the wall-motion analysis, “Cardiac Explorer” (both Philips Medical Systems, Best, The Netherlands). LV function and volumes were quantified using the Simpson rule. Segmental analysis was performed by using a modified AHA 17-segment model, excluding the apex . In the short axis views endocardial and epicardial contours were drawn into representative planes and traced. Segmental wall thickening (SWT) was calculated for every segment by the following formula:
S W T = max . wall thickness – min . wall thickness / max . wall thickness * 100 %
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