Daniel S. Knight

Accuracy and Reproducibility of Right Ventricular Quantification in Patients with Pressure and Volume Overload Using Single-Beat Three-Dimensional Echocardiography

Background The right ventricle is a complex structure that is challenging to quantify by two-dimensional (2D) echocardiography. Unlike disk summation three-dimensional (3D) echocardiography (3DE), single-beat 3DE can acquire large volumes at high volume rates in one cardiac cycle, avoiding stitching artifacts or long breath-holds. The aim of this study was to assess the accuracy and test-retest reproducibility of single-beat 3DE for quantifying right ventricular (RV) volumes in adult populations of acquired RV pressure or volume overload, namely, pulmonary hypertension (PH) and carcinoid heart disease, respectively. Three-dimensional and 2D echocardiographic indices were also compared for identifying RV dysfunction in PH. Methods A prospective cross-sectional study was performed in 100 individuals who underwent 2D echocardiography, 3DE, and cardiac magnetic resonance imaging: 49 patients with PH, 20 with carcinoid heart disease, 11 with metastatic carcinoid tumors without cardiac involvement, and 20 healthy volunteers. Two operators performed test-retest acquisition and postprocessing for inter- and intraobserver reproducibility in 20 subjects. Results: RV single-beat 3DE was attainable in 96% of cases, with mean volume rates of 32 to 45 volumes/sec. Bland-Altman analysis of all subjects (presented as mean bias ± 95% limits of agreement) revealed good agreement for end-diastolic volume (−2.3 ± 27.4 mL) and end-systolic volume (5.2 ± 19.0 mL) measured by 3DE and cardiac magnetic resonance imaging, with a tendency to underestimate stroke volume (−7.5 ± 23.6 mL) and ejection fraction (−4.6 ± 13.8%) by 3DE. Subgroup analysis demonstrated a greater bias for volumetric underestimation, particularly in healthy volunteers (end-diastolic volume, −11.9 ± 18.0 mL; stroke volume, −11.2 ± 20.2 mL). Receiver operating characteristic curve analysis showed that 3DE-derived ejection fraction was significantly superior to 2D echocardiographic parameters for identifying RV dysfunction in PH (sensitivity, 94%; specificity, 88%; area under the curve, 0.95; P = .031). There was significant interobserver test-retest bias for RV volume underestimation (end-diastolic volume, −12.5 ± 28.1 mL; stroke volume, −10.6 ± 23.2 mL). Conclusions Single-beat 3DE is feasible and clinically applicable for volumetric quantification in acquired RV pressure or volume overload. It has improved limits of agreement compared with previous disk summation 3D echocardiographic studies and has incremental value over standard 2D echocardiographic measures for identifying RV dysfunction. Despite the ability to obtain and postprocess a full-volume 3D echocardiographic RV data set, the quality of the raw data did influence the accuracy of the data obtained. The technique performs better with dilated rather than nondilated RV cavities, with a learning curve that might affect the test-retest reproducibility for serial RV studies.

Self-navigated tissue phase mapping using a golden-angle spiral acquisition - Proof of concept in patients with pulmonary hypertension

To create a high temporal‐ and spatial‐resolution retrospectively cardiac‐gated, tissue phase mapping (TPM) sequence, using an image‐based respiratory navigator calculated from the data itself.

Assessment of cardiac time intervals using high temporal resolution real‐time spiral phase contrast with UNFOLDed‐SENSE

To develop a real‐time phase contrast MR sequence with high enough temporal resolution to assess cardiac time intervals.

Accuracy and Test-Retest Reproducibility of Two-Dimensional Knowledge-Based Volumetric Reconstruction of the Right Ventricle in Pulmonary Hypertension

Background Right heart function is the key determinant of symptoms and prognosis in pulmonary hypertension (PH), but the right ventricle has a complex geometry that is challenging to quantify by two-dimensional (2D) echocardiography. A novel 2D echocardiographic technique for right ventricular (RV) quantitation involves knowledge-based reconstruction (KBR), a hybrid of 2D echocardiography–acquired coordinates localized in three-dimensional space and connected by reference to a disease-specific RV shape library. The aim of this study was to determine the accuracy of 2D KBR against cardiac magnetic resonance imaging in PH and the test-retest reproducibility of both conventional 2D echocardiographic RV fractional area change (FAC) and 2D KBR. Methods Twenty-eight patients with PH underwent same-day echocardiography and cardiac magnetic resonance imaging. Two operators performed serial RV FAC and 2D KBR acquisition and postprocessing to assess inter- and intraobserver test-retest reproducibility. Results Bland-Altman analysis (mean bias ± 95% limits of agreement) showed good agreement for end-diastolic volume (3.5 ± 25.0 mL), end-systolic volume (0.9 ± 19.9 mL), stroke volume (2.6 ± 23.1 mL), and ejection fraction (0.4 ± 10.2%) measured by 2D KBR and cardiac magnetic resonance imaging. There were no significant interobserver or intraobserver test-retest differences for 2D KBR RV metrics, with acceptable limits of agreement (interobserver end-diastolic volume, −0.9 ± 21.8 mL; end-systolic volume, −1.3 ± 25.8 mL; stroke volume, −0.2 ± 24.2 mL; ejection fraction, 0.7 ± 14.4%). Significant test-retest variability was observed for 2D echocardiographic RV areas and FAC. Conclusions Two-dimensional KBR is an accurate, novel technique for RV volumetric quantification in PH, with superior test-retest reproducibility compared with conventional 2D echocardiographic RV FAC.

Full left ventricular coverage is essential for the accurate quantification of the area-at-risk by T1 and T2 mapping

T2-weighted cardiovascular magnetic resonance (CMR) using a 3-slice approach has been shown to accurately quantify the edema-based area-at-risk (AAR) in ST-segment elevation myocardial infarction (STEMI). We aimed to compare the performance of a 3-slice approach to full left ventricular (LV) coverage for the AAR by T1 and T2 mapping and MI size. Forty-eight STEMI patients were prospectively recruited and underwent a CMR at 4 ± 2 days. There was no difference between the AARfull LV and AAR3-slices by T1 (P = 0.054) and T2-mapping (P = 0.092), with good correlations but small biases and wide limits of agreements (T1-mapping: N = 30, R2 = 0.85, bias = 1.7 ± 9.4% LV; T2-mapping: N = 48, R2 = 0.75, bias = 1.7 ± 12.9% LV). There was also no significant difference between MI size3-slices and MI sizefull LV (P = 0.93) with an excellent correlation between the two (R2 0.92) but a small bias of 0.5% and a wide limit of agreement of ±7.7%. Although MSI was similar between the 2 approaches, MSI3-slices performed poorly when MSI was <0.50. Furthermore, using AAR3-slices and MI sizefull LV resulted in ‘negative’ MSI in 7/48 patients. Full LV coverage T1 and T2 mapping are more accurate than a 3-slice approach for delineating the AAR, especially in those with MSI < 0.50 and we would advocate full LV coverage in future studies.

001 Multiparametric mapping to understand pathophysiology in cardiac amyloidosis

Background The prognosis and treatment of the 2 main types of cardiac amyloidosis, immunoglobulin light chain (AL) and transthyretin (ATTR) amyloidosis are substantially influenced by cardiac involvement. ATTR amyloidosis has better prognosis than AL despite more amyloid infiltration. This paradox suggests additional mechanisms of damage in AL amyloidosis. The aim of this study was to assess the presence and ?prognostic significance of oedema in a large population of patients with cardiac amyloidosis and compare findings among those with TTR and AL types. Methods and results 286 patients (100 with systemic AL amyloidosis (including 49 patients scanned prior to commencing chemotherapy), 163 with cardiac ATTR amyloidosis, 12 with suspected cardiac ATTR amyloidosis (grade 1 on 99mTc-DPD) and 11 asymptomatic individuals with amyloidogenic transthyretin(TTR) mutations), and 30 healthy volunteers were recruited. All subjects underwent CMR with T1 and T2 mapping, and ECV quantification. Left ventricular(LV) mass and ECV were higher in ATTR compared to AL whilst LV ejection fraction(EF) was significantly lower(p<0.001). There was no significant difference in ECV between treated and untreated AL (Figure 1a). T2 was increased in cardiac amyloidosis compared to healthy volunteers with the degree of elevation being the highest in untreated AL patients (T2: 56.3±4.9 ms AL untreated, 54.0 ±4.5 ms AL treated, 54.3±4.1 ms ATTR, 48.9±2.0 ms controls, p<0.05 for all except treated AL vs ATTR) (Figure 1b). During follow up (22.8±14.7 months), 75 (28% of AL group and 25% of ATTR group) patients died. Using Cox regression models, T2 predicted death in AL amyloidosis (hazard ratio, HR,1.48, 95% CI 1.20–1.82) and remained significant after adjusting for EF and ECV (HR 1.31, 95% CI 1.04–1.66) (Abstract 1 Figure 2). Abstract 001 Figure 1 a. Mean ECV in cardiac AL (treated and untreated patients) and ATTR amyloidosis compared to healthy volunteers. b. Mean T2 in cardiac AL (treated and untreated patients) and ATTR amyloidosis compared to healthy volunteers. Abstract 001 Figure 2 a. Examples of two patients with AL amyloidosis and transmural late gadolinium enhancement, one with eleveted T2 (top) and the other with normal T2 (bottom). b. Kaplan-Meier survival curve of patients with AL amyloidosis with high T2 and normal T2 values. Conclusion Patients with AL amyloidosis have a worse prognosis compared to ATTR despite having less cardiac amyloid infiltration. T2 was significantly higher in untreated AL amyloidosis consistent with oedema, and was an independent predictor of prognosis. The higher ECV in ATTR was consistent with higher amyloid infiltration. These findings highlight the unique role of CMR with multiparametric mapping for characterising the cardiac effects of systemic amyloidosis and risk stratification in this population.

CMR-Verified Regression of Cardiac AL Amyloid After Chemotherapy

Systemic light-chain (AL) amyloidosis is characterized by interstitial deposition of aggregated misfolded monoclonal immunoglobulin light chains in the form of amyloid fibrils. Cardiac involvement is the main driver of prognosis. Brain natriuretic peptides and echocardiography are currently the

Prospective comparison of novel dark blood late gadolinium enhancement with conventional bright blood imaging for the detection of scar

BackgroundConventional bright blood late gadolinium enhancement (bright blood LGE) imaging is a routine cardiovascular magnetic resonance (CMR) technique offering excellent contrast between areas of LGE and normal myocardium. However, contrast between LGE and blood is frequently poor. Dark blood LGE (DB LGE) employs an inversion recovery T2 preparation to suppress the blood pool, thereby increasing the contrast between the endocardium and blood. The objective of this study is to compare the diagnostic utility of a novel DB phase sensitive inversion recovery (PSIR) LGE CMR sequence to standard bright blood PSIR LGE.MethodsOne hundred seventy-two patients referred for clinical CMR were scanned. A full left ventricle short axis stack was performed using both techniques, varying which was performed first in a 1:1 ratio. Two experienced observers analyzed all bright blood LGE and DB LGE stacks, which were randomized and anonymized. A scoring system was devised to quantify the presence and extent of gadolinium enhancement and the confidence with which the diagnosis could be made.ResultsA total of 2752 LV segments were analyzed. There was very good inter-observer correlation for quantifying LGE. DB LGE analysis found 41.5% more segments that exhibited hyperenhancement in comparison to bright blood LGE (248/2752 segments (9.0%) positive for LGE with bright blood; 351/2752 segments (12.8%) positive for LGE with DB; p < 0.05). DB LGE also allowed observers to be more confident when diagnosing LGE (bright blood LGE high confidence in 154/248 regions (62.1%); DB LGE in 275/324 (84.9%) regions (p < 0.05)). Eighteen patients with no bright blood LGE were found to have had DB LGE, 15 of whom had no known history of myocardial infarction.ConclusionsDB LGE significantly increases LGE detection compared to standard bright blood LGE. It also increases observer confidence, particularly for subendocardial LGE, which may have important clinical implications.

Novel magnetic resonance wave intensity analysis in pulmonary hypertension

Background In pulmonary arterial hypertension (PH), abnormal wave reflections play an important part in pathophysiology and can be assessed using wave intensity analysis (WIA). However, conventionally this technique requires simultaneous invasive measurement of pulmonary artery pressure and velocity. Therefore, we have developed a novel non-invasive technique that uses high temporalresolution phase-contrast MR (PCMR) flow and area data to perform WIA. The aim of this study was to establish any differences in wave reflections between patients with PH and healthy volunteers. Methods Right PA volume flow and area curves were obtained in 15 patients with PH (mean ± SD, age 52 ± 13 years) and 10 healthy controls (age 45 ± 11 years) using a retrospectively gated, respiratory navigated, golden-angle, high TR, PCMR sequence. The right PA was used to avoid the through plane motion in the main PA. All patients also underwent right heart cardiac catheterization for pressure and vascular resistance (PVR) measurement within 30days (mean 11days) and had serum brain natriuretic peptide (BNP) measured. Wave speed was determined in the right PA using the single slice Q-A method. WIA was derived in terms of volume flow and area changes. Results There were significant differences in WIA between cases and controls (Table 1 Figure 1). Wave speed was higher in PH than controls in keeping with reduced arterial compliance (p = 0.0001). A backwards compression wave (BCW) was observed in all patients with PH (Figure 1C), but was absent in all control patients (p < 0.0001). Conversely a backwards expansion wave was seen in normal controls but not in PH. Average PVR and PA mean arterial pressure (MAP) were 612 ± 298 ARU and 43 ± 12 mmHg respectively. There was a significant correlation between MAP and the duration of the BCW (R = 0.62, p = 0.01) and also the ratio of the magnitude of the forward (FCW) and backwards compression waves (R = -0.57, p = 0.03). PVR was independently associated with the acceleration time (AT, Figure 1A) (b = -1.42,

Redefining viability by cardiovascular magnetic resonance in acute ST-segment elevation myocardial infarction

In chronic myocardial infarction (MI), segments with a transmural extent of infarct (TEI) of ≤50% are defined as being viable. However, in the acute phase of an ST-segment elevation myocardial infarction (STEMI), late gadolinium enhancement (LGE) has been demonstrated to overestimate MI size and TEI. We aimed to identify the optimal cut-off of TEI by cardiovascular magnetic resonance (CMR) for defining viability during the acute phase of an MI, using ≤50% TEI at follow-up as the reference standard. 40 STEMI patients reperfused by primary percutaneous coronary intervention (PPCI) underwent a CMR at 4 ± 2 days and 5 ± 2 months. The large majority of segments with 1–25%TEI and 26–50%TEI that were viable acutely were also viable at follow-up (59/59, 100% and 75/82, 96% viable respectively). 56/84(67%) segments with 51–75%TEI but only 4/63(6%) segments with 76–100%TEI were reclassified as viable at follow-up. TEI on the acute CMR scan had an area-under-the-curve of 0.87 (95% confidence interval of 0.82 to 0.91) and ≤75%TEI had a sensitivity of 98% but a specificity of 66% to predict viability at follow-up. Therefore, the optimal cut-off by CMR during the acute phase of an MI to predict viability was ≤75% TEI and this would have important implications for patients undergoing viability testing prior to revascularization during the acute phase.