Magnetic resonance-derived circumferential strain provides a superior and incremental assessment of improvement in contractile function in patients early after ST-segment elevation myocardial infarction.

BACKGROUND: We evaluate whether circumferential strain derived from grid-tagged CMR is a better method for assessing improvement in segmental contractile function after STEMI compared to late gadolinium enhancement (LGE). METHODS: STEMI patients post primary PCI underwent baseline CMR (day 3) and follow-up (day 90). Cine, grid-tagged and LGE images were acquired. Baseline LGE infarct hyperenhancement was categorised as ≤25 %, 26-50 %, 51-75 % and >75 % hyperenhancement. The segmental baseline circumferential strain (CS) and circumferential strain rate (CSR) were calculated from grid-tagged images. Segments demonstrating an improvement in wall motion of ≥1 grade compared to baseline were regarded as having improved segmental contractile-function. RESULTS: Forty-five patients (aged 58 ± 12 years) and 179 infarct segments were analysed. A baseline CS cutoff of -5 % had sensitivity of 89 % and specificity of 70 % for detection of improvement in segmental-contractile-function. On receiver-operating characteristic analysis for predicting improvement in contractile function, AUC for baseline CS (0.82) compared favourably to LGE hyperenhancement (0.68), MVO (0.67) and baseline-CSR (0.74). On comparison of AUCs, baseline CS was superior to LGE hyperenhancement and MVO in predicting improvement in contractile function (P < 0.001). On multivariate-analysis, baseline CS was the independent predictor of improvement in segmental contractile function (P < 0.001). CONCLUSION: Grid-tagged CMR-derived baseline CS is a superior predictor of improvement in segmental contractile function, providing incremental value when added to LGE hyperenhancement and MVO following STEMI. KEY POINTS: Baseline CS predicts contractile function recovery better than LGE and MVO following STEMI. Baseline CS predicts contractile function recovery better than baseline CSR following STEMI. Baseline CS provides incremental value to LGE and MVO following STEMI.

Comparison of diagnostic accuracy of combined assessment using adenosine stress computed tomography perfusion + computed tomography angiography with transluminal attenuation gradient + computed tomography angiography against invasive fractional flow reserve.

OBJECTIVES: The goal of this study was to compare the diagnostic accuracy of combined computed tomography perfusion (CTP) + computed tomography angiography (CTA), transluminal attenuation gradient by 320-detector row computed tomography (TAG320) + CTA, and CTP + TAG320 + CTA (multidetector computed tomography-integrated protocol [MDCT-IP]) assessment in predicting significant fractional flow reserve (FFR). BACKGROUND: CTA has limited specificity for predicting functionally significant stenoses. Novel CT techniques, including adenosine stress CTP and TAG320, may improve the diagnostic accuracy of CTA. METHODS: CTA, CTP, and TAG320 were assessed using 320-detector row MDCT. Patients who underwent CTA, CTP, and FFR assessment on invasive coronary angiography were included. CTP was assessed using the visual perfusion assessment. TAG320 was defined as the linear regression coefficient between luminal attenuation and axial distance. A TAG320 cutoff value of -15.1 HU/10 mm as previously described was defined as significant. Functionally significant coronary stenosis was defined as FFR ≤0.8. RESULTS: The cohort included 75 patients (age 64.1 ± 10.8 years, 52 men) and 44 (35%) FFR-significant vessels. In 127 vessels, CTA predicted FFR-significant stenosis with 89% sensitivity and 65% specificity compared with MDCT-IP, which showed 88% sensitivity and 83% specificity. In 97 vessels in which the results of all techniques were available, TAG320 + CTA (area under the curve [AUC] = 0.844) and CTP + CTA (AUC = 0.845) had comparable per-vessel diagnostic accuracy (p = 0.98). The diagnostic accuracy of MDCT-IP (AUC = 0.91) was superior to TAG320 + CTA or CTP + CTA (p = 0.01). CONCLUSIONS: In vessels without significant calcification or artefact, TAG320 + CTA and CTP + CTA provide comparable diagnostic accuracy for functional assessment of coronary artery stenosis. MDCT-IP may provide the best diagnostic accuracy for functional assessment of coronary artery stenosis.

Cardiac magnetic resonance derived late microvascular obstruction assessment post ST-segment elevation myocardial infarction is the best predictor of left ventricular function: a comparison of angiographic and cardiac magnetic resonance derived measurements.

Microvascular obstruction (MVO) is a strong independent predictor of left ventricular remodelling and mortality following ST-segment elevation myocardial infarction (STEMI). Microvascular obstruction can be identified at angiography or with gadolinium-enhanced cardiac MRI (CMR). First-pass perfusion CMR also allows a novel quantitative evaluation of myocardial blood flow (MBF) that might provide superior predictive data in the assessment of MVO. We sought to compare angiographic and CMR derived methodologies in the assessment of MVO to determine the optimal methodology that best predicts the surrogate outcome marker of left ventricular function post STEMI. Following primary-PCI angiographic assessment of 'no-reflow' with TIMI myocardial perfusion grade (TMPG) and myocardial blush grade (MBG) were documented. Assessment of CMR derived MVO was assessed on day 3, with MVO on first-pass perfusion imaging termed 'early MVO' and on late gadolinium enhancement, 'late MVO'. Furthermore on the same day 3 CMR scan, myocardial blood flow in the infarct region was quantified at adenosine stress and rest utilizing standard perfusion imaging sequences. Assessment of remodelling, structure and function was undertaken via standard CMR imaging assessment on day 90 post-STEMI and was used as the surrogate marker for long term clinical outcome. Forty patients (age 59 ± 12 years, 84% males) were appraised. Late MVO had the strongest correlation with LVEF at 90 days compared to the CMR parameters of early MVO, stress infarct region MBF and rest infarct region MBF (r = -0.754, r = -0.588, r = 0.595 and r = 0.345 respectively). Of the angiographic parameters used to assess MVO, TMPG had the strongest relationship with MVO when assessed via CMR. Myocardial blush grade however showed no relationship to CMR derived assessment of MVO. On multivariate analysis, of all angiographic and CMR variables, late MVO was the strongest predictor of LVEF at 90 days (p = 0.004). Cardiac magnetic resonance imaging derived assessment of microvascular obstruction on late gadolinium enhancement strongly predicts left ventricular function following STEMI at 90 days.