Simultaneous right and left heart real-time, free-breathing CMR flow quantification identifies constrictive physiology

Abstract

Objectives: The purpose of this study was to evaluate the ability of a novel cardiac magnetic resonance (CMR) real-time phase contrast (RT-PC) flow measurement technique to reveal the discordant respirophasic changes in mitral and tricuspid valve in flow indicative of the abnormal hemodynamics seen in constrictive pericarditis (CP).

Background: Definitive diagnosis of CP requires identification of constrictive hemodynamics with or without pericardial thickening. CMR to date has primarily provided morphological assessment of the pericardium.

Methods: Sixteen patients (age 57 ± 13 years) undergoing CMR to assess known or suspected CP and 10 controls underwent RT-PC that acquired simultaneous mitral valve and tricuspid valve inflow velocities over 10 s of unrestricted breathing. The diagnosis of CP was confirmed via clinical history, diagnostic imaging, cardiac catheterization, intraoperative findings, and histopathology.

Results: Ten patients had CP, all with increased pericardial thickness (6.2 ± 1.0 mm). RT-PC imaging demonstrated discordant respirophasic changes in atrioventricular valve inflow velocities in all CP patients, with mean ± SD mitral valve and tricuspid valve inflow velocity variation of 46 ± 20% and 60 ± 15%, respectively, compared with 16 ± 8% and 24 ± 11% in patients without CP (p < 0.004 vs. patients with CP for both) and 17 ± 5% and 31 ± 13% in controls (p < 0.001 vs. patients with CP for both). There was no difference in atrioventricular valve inflow velocity variation between patients without CP compared with controls (p > 0.3 for both). Respiratory variation exceeding 25% across the mitral valve yielded a sensitivity of 100%, a specificity of 100%, and an area under the receiver-operating characteristic curve of 1.0 to detect CP physiology. Using a cutoff of 45%, variation of transtricuspid valve velocity had a sensitivity of 90%, a specificity of 88%, and an area under the receiver-operating characteristic curve of 0.98.

Conclusions: Accentuated and discordant respirophasic changes in mitral valve and tricuspid valve inflow velocities characteristic of CP can be identified noninvasively with RT-PC CMR. When incorporated into existing CMR protocols for imaging pericardial morphology, RT-PC CMR provides important hemodynamic evidence with which to make a definite diagnosis of CP.

Figure 1. RT-PC Acquired Across MV and TV

(A) Diastolic frame from a horizontal long-axis cine acquisition shows how the plane for through-plane real-time phase-contrast (RT-PC) imaging was prescribed. Resulting magnitude (B) and phase (C) images from RT-PC imaging are shown. Regions of interest for the mitral valve (MV) (red) and tricuspid valve (TV) (green) are illustrated in both the phase and magnitude images.

Figure 2. Respirophasic Variation in MV and TV Inflow Velocities by RT-PC CMR

Two representative examples of RT-PC velocities across MV (red bars) and TV (green bars) show respirophasic variation, and the same patients’ corresponding dark blood images (half Fourier single-shot turbo spin echo and T1-weighted turbo spin echo) illustrate thickened pericardium. (A and B) Represent patients #8 and #3 from Table 2. Patient #3’s heart rate was 103 beats/min at acquisition resulting in E and A fusion (B). A = late mitral diastolic peak velocity; CMR = cardiac magnetic resonance; E = early mitral diastolic peak velocity; Exp = expiratory; Insp = inspiratory; other abbreviations as in Figure 1.

Figure 3. Comprehensive Assessment of Patient #10 With Surgically Proven Constrictive Pericarditis

(A and B) Cardiac computed tomography images show extensive pericardial calcification (arrows). (C) Transmitral Doppler inflow illustrates a restrictive ventricular filling pattern (E/A >2.0, DT 149 ms). (D) Lateral mitral annulus tissue velocity demonstrates increased early mitral anular velocity (E′) velocity of 16 cm/s. (E) Simultaneous left and right heart catheterization demonstrates equalization of end-diastolic pressures (right ventricular [RV] end-diastolic pressure – left ventricular [LV] end-diastolic pressure ≤5 mm Hg), dip and plateau pattern of ventricular diastolic pressures, and ventricular interdependence (systolic area index 1.4). (F) Simultaneous LV and pulmonary capillary wedge pressure (PCWP) illustrating >5 mm Hg change in the gradient between inspiration and expiration, a sign of dissociation between intrathoracic and intracardiac pressures. (G) CMR real-time simultaneously measured transmitral and trans-TV flows (TV [green], MV [red]). (H) Dark blood half Fourier single-shot turbo spin echo coronal image shows thickened pericardium (arrows). Please see Online Videos 1 and 2. DT = deceleration time; other abbreviations as in Figures 1 and 2.

Figure 4. Excluding Pericardial Constriction by RT-PC CMR

RT-PC trans-MV (red) and TV (green) flow velocity curves are shown from a patient without constrictive pericarditis (A) and a healthy control (B). Patient A was a 56-year-old woman and patient B was a 29-year-old man. Both lack the characteristic discordant flow pattern relative to the respiratory cycle seen in patients with constrictive pericarditis. DT = deceleration time; other abbreviations as in Figures 1 and 2.

Figure 5. Post-Pericardiectomy Improvement in Constrictive Hemodynamics

Histology and repeat CMR findings from patient #3 include histology of the thick pericardium with fibrous tissue and inflammation on hematoxylin and eosin staining (A). (B) Coronal plane half Fourier single-shot turbo spin echo image shows no residual thickened pericardium. (C) RT-PC MV and TV inflows illustrate resolution of the respirophasic flow variation that was seen preoperatively (Fig. 2B). The heart rate at acquisition was 112 beats/min, resulting in E and A fusion. Please see Online Video 3. Abbreviations as in Figures 1 and 2.

Figure 6. Receiver-Operating Characteristic Curves Comparing Patients With Constriction and Patients Without Constriction and Controls

MV inflow variation of 25% had a sensitivity of 100%, a specificity of 100%, and an area under the curve of 1.0. For TV inflow variation of 45%, the sensitivity, specificity, and area under the curve were 90%, 88%, and 0.98, respectively. Abbreviations as in Figure 1.