Myocardial dysfunction in patients with aortic stenosis and hypertensive heart disease assessed by MR tissue phase mapping.

PURPOSE: To identify abnormalities of myocardial velocities in patients with left ventricular pressure overload using magnetic resonance tissue phase mapping (TPM). MATERIAL AND METHODS: Thirty-three patients (nine with hypertensive heart disease [HYP], 24 with aortic stenosis [AS]) and 41 healthy controls were enrolled. To assess left ventricular motion, a basal, midventricular, and apical slice were acquired using three-directional velocity-encoded phase-contrast MR with a 3T system. Target parameters were peak longitudinal (Vz ) and radial (Vr ) velocity in systole and diastole (Peaksys , Peakdias ). Analysis was done on each myocardial segment. In a subgroup (n = 7 HYP, n = 12 AS, n = 24 controls), measurement was repeated during handgrip exercise. RESULTS: AS had significantly lower Vz -Peaksys in the inferolateral and inferoseptal wall (P = 0.003-0.029) and Vr -Peaksys in the septum and anterior wall (P = 0.001-0.013) than controls. Vz -Peakdias and Vr -Peakdias were lower in AS than in controls in almost all segments (P < 0.001-0.028). HYP showed reduced Vz -Peakdias compared to controls in all basal segments as well as in the lateral midventricular wall (P < 0.001-0.045), and reduced Vr -Peakdias compared to controls predominantly in the midventricular and apical segments (P = 0.004-0.042). AS patients with focal fibrosis had significantly reduced myocardial velocities (P = 0.001-0.047) in segments without late enhancement. During exercise, Vz -Peaksys , Vr -Peaksys , and Vz -Peakdias remained unchanged in AS and HYP, but decreased in the lateral wall in controls (P < 0.001-0.043). CONCLUSION: Even with preserved left ventricle (LV) ejection fraction, peak longitudinal and radial velocities of the LV are reduced in AS and HYP, indicating early functional impairment. J. Magn. Reson. Imaging 2016;44:168-177.

Myocardial T2-mapping and velocity mapping: changes in regional left ventricular structure and function after heart transplantation.

Monitoring post cardiac transplant (TX) status relies on frequent invasive techniques such as endomyocardial biopsies and right heart cardiac catheterization. The aim of this study was to noninvasively evaluate regional myocardial structure, function, and dyssynchrony in TX patients. Myocardial T2-mapping and myocardial velocity mapping of the left ventricle (basal, midventricular, and apical short-axis locations) was applied in 10 patients after cardiac transplantation (49 ± 13 years, n = 2 with signs of mild rejection, time between TX and MRI = 1-64 months) and compared to healthy controls (n = 20 for myocardial velocity mapping and n = 14 for T2). Segmental analysis based on the 16-segment American Heart Association model revealed increased T2 (P = 0.0003) and significant (P < 0.0001) reductions in systolic and diastolic radial and long-axis peak myocardial velocities in TX patients without signs of rejection compared to controls. Multiple comparisons of individual left ventricular segments demonstrated reductions of long-axis peak velocities in 50% of segments (P < 0.001) while segmental T2 values were not significantly different. Systolic radial as well as diastolic radial and long-axis dyssynchrony were significantly (P < 0.04) increased in TX patients indicating less coordinated contraction, expansion, and lengthening. Correlation analysis revealed moderate but significant (P < 0.010) inverse relationships between myocardial T2 and long-axis peak velocities suggesting a structure-function relationship between altered T2 and myocardial function.

Segmental myocardial velocities in dilated cardiomyopathy with and without left bundle branch block.

PURPOSE: To quantify three-directional left ventricular (LV) myocardial velocities and intraventricular synchrony in dilated cardiomyopathy (DCM) with and without left bundle branch block (LBBB) using MR tissue phase mapping (TPM). MATERIALS AND METHODS: Regional velocities were assessed by TPM (spatial/temporal resolution = 1.3 × 1.3 mm(2) × 8 mm/14 ms) in DCM patients with (n = 12) and without LBBB (n = 7) compared with age-matched volunteers (n = 20). For the evaluation the AHA 16-segment and an extended LV visualization model was used. RESULTS: Radial velocities in DCM patients were reduced in 75% (systole) and in 94% (diastole) (P = 0.0001 - P = 0.0360), long-axis velocities in 31% (systole) and in 75% (diastole) of the 16 segments compared with controls (P = 0.0001 - P = 0.0310). LBBB resulted in inferolaterally delayed diastolic long-axis velocities (P = 0.0012 - P = 0.0464) and shortened TTP for septal systolic radial velocities (P = 0.0002). Intra-ventricular radial systolic TTP differed up to 150 ms between segments in patients with LBBB (89 ms without LBBB, 34 ms in volunteers) reflecting an increased dyssynchrony. LV twist was altered in all patients with reduced and delayed systolic and diastolic peak velocities. CONCLUSION: TPM identified previously not described alterations of the spatial distribution and timing of all myocardial velocities in patients with DCM and LBBB. This may help to optimize therapy management in future.

Three-dimensional echocardiography for quantitative analysis of left-ventricular aneurysm.

BACKGROUND: Quantitative analysis of left-ventricular (LV) aneurysms after myocardial infarction is prognostically relevant and assists in planning surgery. Three-dimensional (3D) echocardiography facilitates clear visualization of cardiac anatomy and accurate assessment of functional parameters. The aim of the present study was to determine the ability of 3D echocardiography to quantify LV aneurysms. METHODS: Ten patients with a known LV-aneurysm after myocardial infarction underwent 3D echocardiography and cardiac magnetic resonance (CMR) imaging at 1.5 Tesla within 3 days. For 3D echocardiography, a multiplanar transesophageal examination was performed with full LV coverage and the 3D dataset was analyzed offline. The LV-aneurysm was defined by a wall thickness <5 mm. The following quantitative parameters were determined: left ventricular end-diastolic and end-systolic volumes, LV myocardial mass (LV-mass) and mass of the LV-aneurysm. LV ejection fraction and percentage of aneurysm mass (%-aneurysm) were calculated. RESULTS: LV volumes and ejection fraction showed a strong correlation between 3D echocardiography and CMR (r = 0.94-0.97; P < 0.01). Importantly, the mass and percentage of mass of the LV-aneurysm demonstrated a high correlation as well (r = 0.94 and r = 0.86, respectively; P < 0.01). For all parameters, the calculated bias between both methods was found to be minimal (0.8-7.6%). CONCLUSIONS: Three-dimensional echocardiography proved to be a reliable tool for quantitative analysis of LV volumes, ejection fraction and aneurysm size in patients with prior myocardial infarction. In addition, 3D visualization of the complex cardiac anatomy in patients with LV-aneurysm may assist surgical procedure planning.

Electro-mechanical (dys-)function in long QT syndrome type 1.

BACKGROUND: Prolonged repolarization is the hallmark of long QT syndrome (LQTS), which is associated with subclinical mechanical dysfunction. We aimed at elucidating mechanical cardiac function in LQTS type 1 (loss of IKs) and its modification upon further prolongation of the action potential (AP) by IKr-blockade (E-4031). METHODS: Transgenic LQT1 and wild type (WT) rabbits (n = 12/10) were subjected to tissue phase mapping MRI, ECG, and epicardial AP recording. Protein and mRNA levels of ion channels and Ca2+ handling proteins (n = 4/4) were determined. In silico single cell AP and tension modeling was performed. RESULTS: At baseline, QT intervals were longer in LQT1 compared to WT rabbits, but baseline systolic and diastolic myocardial peak velocities were similar in LQT1 and WT. E-4031 prolonged QT more pronouncedly in LQT1. Additionally, E-4031 increased systolic and decreased diastolic peak velocities more markedly in LQT1 - unmasking systolic and diastolic LQT1-specific mechanical alterations. E-4031-induced alterations of diastolic peak velocities correlated with the extent of QT prolongation. CONCLUSION: While baseline mechanical function is normal in LQT1 despite a distinct QT prolongation, further prolongation of repolarization by IKr-blocker E-4031 unmasks mechanical differences between LQT1 and WT with enhanced systolic and impaired diastolic function only in LQT1. These data indicate an importance of the extent of QT prolongation and the contribution of different impaired ion currents for conveying mechanical dysfunction.

Phase-contrast magnet resonance imaging reveals regional, transmural, and base-to-apex dispersion of mechanical dysfunction in patients with long QT syndrome.

BACKGROUND: Regional dispersion of prolonged repolarization is a hallmark of long QT syndrome (LQTS). We have also revealed regional heterogeneities in mechanical dysfunction in transgenic rabbit models of LQTS. OBJECTIVE: In this clinical pilot study, we investigated whether patients with LQTS exhibit dispersion of mechanical/diastolic dysfunction. METHODS: Nine pediatric patients with genotyped LQTS (12.2 ± 3.3 years) and 9 age- and sex-matched healthy controls (10.6 ± 1.5 years) were subjected to phase-contrast magnetic resonance imaging to analyze radial (Vr) and longitudinal (Vz) myocardial velocities during systole and diastole in the left ventricle (LV) base, mid, and apex. Twelve-lead electrocardiograms were recorded to assess the heart rate-corrected QT (QTc) interval. RESULTS: The QTc interval was longer in patients with LQTS than in controls (469.1 ± 39.4 ms vs 417.8 ± 24.4 ms; P < .01). Patients with LQTS demonstrated prolonged radial and longitudinal time-to-diastolic peak velocities (TTP), a marker for prolonged contraction duration, in the LV base, mid, and apex. The longer QTc interval positively correlated with longer time-to-diastolic peak velocities (correlation coefficient 0.63; P < .01). Peak diastolic velocities were reduced in LQTS in the LV mid and apex, indicating impaired diastolic relaxation. In patients with LQTS, regional (TTPmax-min) and transmural (TTPVz-Vr) dispersion of contraction duration was increased in the LV apex (TTPVz_max-min: 38.9 ± 25.5 ms vs 20.2 ± 14.7 ms; P = .07; TTPVz-Vr: -21.7 ± 14.5 ms vs -8.7 ± 11.3 ms; P < .05). The base-to-apex longitudinal relaxation sequence was reversed in patients with LQTS compared with controls (TTPVz_base-apex: 14.4 ± 14.9 ms vs -10.1 ± 12.7 ms; P < .01). CONCLUSION: Patients with LQTS exhibit diastolic dysfunction with reduced diastolic velocities and prolonged contraction duration. Mechanical dispersion is increased in LQTS with an increased regional and transmural dispersion of contraction duration and altered apicobasal longitudinal relaxation sequence. LQTS is an electromechanical disorder, and phase-contrast magnetic resonance imaging Heterogeneity in mechanical dysfunction enables a detailed assessment of mechanical consequences of LQTS.

Initial experience with 64-slice cardiac CT: non-invasive visualization of coronary artery bypass grafts.

AIMS: The aim of this study was to evaluate the diagnostic accuracy in the assessment of coronary artery bypass grafts using 64-slice computed tomography (CT) technology. METHODS AND RESULTS: CT coronary angiography was performed for 96 bypasses in 31 patients with suspected coronary artery disease using a Siemens Sensation 64-slice CT-scanner and compared with invasive coronary angiography (ICA). Patients with an irregular or fast heart rate despite beta-blocker administration were not excluded from the study. All bypass grafts and 94% of the distal bypass anastomoses could be visualized by CT, non-evaluable distal arterial anastomoses were either due to clip material or calcification artefacts. Forty-two bypass graft occlusions and three significant stenoses were detected by CT and confirmed by ICA. Two venous grafts were missed and one arterial graft was not evaluable with ICA, but both were clearly depicted by multi-slice CT. One false negative and two false positive CT-findings resulted in a sensitivity of 97.8%, a specificity of 89.3%, a positive predictive value of 90%, and a negative predictive value of 97.7%. CONCLUSION: State-of-the-art 64-slice CT coronary angiography demonstrates high diagnostic accuracy in the assessment of arterial and venous bypass graft stenoses.

Computed tomography coronary angiography with 370-millisecond gantry rotation time: evaluation of the best image reconstruction interval.

OBJECTIVE: To evaluate the best reconstruction window for noninvasive coronary angiography when using a 16-detector row computed tomography (CT) scanner with a gantry rotation time of 370 milliseconds. METHODS: In a pilot study, 189 coronary artery segments of 21 patients with a mean heart rate of 65 beats per minute (bpm, maximum: 45-94 bpm) were investigated using a 16-detector row CT scanner. Raw data were reconstructed in 10% increments from 40% to 70% of the RR interval. Two experienced observers independently evaluated the image quality of the coronary arteries in a segmental fashion. A 5-point ranking scale was applied, with 1 being very poor (no evaluation possible); 2, poor; 3, moderate; 4, good; and 5, very good. RESULTS: In the mean of all patients, the best reconstruction window was found to be at 60% of the RR interval. In patients with higher heart rates, the best reconstruction window was found to be at an earlier stage of the R wave-to-R wave interval. CONCLUSIONS: Initial results show that good diagnostic image quality could be achieved for all evaluated segments of the coronary tree with image reconstructions at 60% of the R wave-to-R wave interval in patients with heart rates of 70 bpm or less. Using a 16-detector row CT scanner with a gantry rotation time of 370 milliseconds, the need for adapting the reconstruction window to each segment for the best image quality was overcome in those cases. In patients with heart rates faster than 70 bpm, reconstructions at an earlier stage within the cardiac cycle were necessary.

Safety and feasibility of high-dose dobutamine-atropine stress cardiovascular magnetic resonance for diagnosis of myocardial ischaemia: experience in 1000 consecutive cases.

AIMS: To determine the safety of high-dose dobutamine-atropine stress cardiovascular magnetic resonance (stress-CMR), which recently emerged as a highly accurate modality for diagnosis of inducible myocardial ischaemia. METHOD AND RESULTS: From 1997 to 2002, 1000 consecutive stress-CMR examinations were performed. Images were acquired at rest and during a high-dose dobutamine-atropine protocol in 3 short-axis, a 4- and a 2-chamber view. Stress testing was discontinued when > or =85% of age-predicted heart rate was reached, on patient request, maximum pharmacologic infusion, or when new or worsening wall motion abnormalities, severe angina, dyspnoea, increase or decrease in blood pressure, or severe arrhythmias occurred. Stress-CMR was successfully performed in all but four patients (0.4%; insufficient ECG-triggering). Target heart rate was not reached in 95 cases (9.5%), due to maximum pharmacologic infusion in submaximal negative examinations in 21 cases (2.1%), and limiting side effects in 74 (7.4%). Side effects included one case (0.1%) of sustained and four cases (0.4%) of non-sustained ventricular tachycardia, 16 cases (1.6%) of atrial fibrillation, and two cases (0.2%) of transient second degree AV block. CONCLUSION: The safety profile of stress-CMR is similar to other methodologies using dobutamine infusions. Patients must be closely monitored, and resuscitation equipment and trained personnel must be available.