Peter J. Cawley

Cardiovascular magnetic resonance imaging for valvular heart disease: technique and validation.

Over the last half century, clinicians have employed several means to advance our knowledge of the causes and consequences of valvular heart disease. Invasive cardiac catheterization provided valuable information about hemodynamics, 2-dimensional (2D) echocardiography (echo) allowed direct visualization of the valvular apparatus and cardiac chambers, and Doppler echocardiography afforded a noninvasive tool for assessing hemodynamics and disease severity. Echocardiography is now the standard tool for initial assessment and longitudinal evaluation of patients with valvular heart disease; however, echocardiography is limited in patients with poor acoustic windows and may be more operator dependent than other modalities, particularly for quantitation of disease severity. In the last 20 years, cardiovascular magnetic resonance (CMR) has emerged as an alternative noninvasive modality without ionizing radiation that is applicable to patients with valvular heart disease. CMR provides images of valve anatomy and allows quantitative evaluation of stenosis and regurgitation. CMR can also discern the consequences of the valvular lesion, including the effects of ventricular volume or pressure overload and alterations in systolic function. The purpose of the present review is to summarize the general principles of CMR and validate CMR as a tool for evaluation of valvular heart disease. CMR uses a variety of pulse sequences to assess valvular heart disease (Table 1). A pulse sequence is a combination of transmitted radiofrequency pulses and magnetic gradients in the presence of a strong external magnetic field, from which a series of received radiofrequency pulses or “echoes” are obtained and processed into an image.1,2 View this table: Table 1. CMR Pulse Sequences for Valvular Heart Disease ### Anatomy CMR has the potential to visualize all parts of the valve (leaflets, chordae tendineae, and papillary muscles) throughout the entire cardiac cycle. Congenitally abnormal valve leaflets (bicuspid), aberrant papillary muscles or aberrant chordal attachments (parachute mitral valve), leaflet thickening, presence and extent of calcification, …

Prospective Comparison of Valve Regurgitation Quantitation by Cardiac Magnetic Resonance Imaging and Transthoracic Echocardiography

Background—Both transthoracic echocardiography (TTE) and cardiac magnetic resonance (CMR) imaging allow quantification of chronic aortic regurgitation (AR) and mitral regurgitation (MR). We hypothesized that CMR measurement of regurgitant volume (RVol) is more reproducible than TTE. Methods and Results—TTE and CMR performed on the same day in 57 prospectively enrolled adults (31 with AR, 26 with MR) were measured by 2 independent physicians. TTE RVolAR was calculated as Doppler left ventricular outflow minus inflow stroke volume. RVolMR was calculated by both the proximal isovelocity surface area method and Doppler volume flow at 2 sites. CMR RVolAR was calculated by phase-contrast velocity mapping at the aortic sinuses and RVolMR as total left ventricular minus forward stroke volume. Intraobserver and interobserver variabilities were similar. For AR, the Bland–Altman mean interobserver difference in RVol was −0.7 mL (95% confidence interval [CI], −5 to 4) for CMR and −9 mL (95% CI, −53 to −36) for TTE. The Pearson correlation was higher (P=0.001) between CMR (0.99) than TTE readers (0.89). For MR, the Bland–Altman mean difference in RVol between observers was −4 mL (95% CI, −21 to 13) for CMR compared with 0.7 mL (95% CI, −30 to 32) for the proximal isovelocity surface area and −10 mL (95% CI, −76 to 56) for TTE volume flow at 2 sites. Correlation was similar for CMR (0.94) versus TTE readers (0.90 for the proximal isovelocity surface area). Conclusions—Compared with TTE, CMR has lower intraobserver and interobserver variabilities for RVolAR, suggesting CMR may be superior for serial measurements. Although RVolMR is similar by TTE and CMR, variability in measured RVol by both approaches suggests that caution is needed in clinical practice.

Prevention of calcific aortic valve stenosis—fact or fiction?

Valve replacement is the only long-term effective treatment for calcific aortic valve stenosis. However, this treatment is aimed only at patients with advanced leaflet disease and symptoms of left ventricular obstruction. Over the past 15 years, our understanding of the pathogenesis of calcific aortic stenosis has changed significantly: away from a passive degenerative disease to an active process involving endothelial dysfunction, lipid accumulation, an inflammatory infiltrate, and a regulated process of calcification. Since many of the same processes are characteristic of atherosclerosis, trials have been undertaken to test whether medical therapy (statins, renin-angiotensin inhibition) can prevent or alter the disease course. Although retrospective and non-randomized studies suggested a positive effect with statins, benefit has not been seen in perspective randomized controlled trials, although two major studies are still in progress. Inhibition of renin-angiotensin has shown discordant results in retrospective studies with no randomized controlled data published. In the future, we need to consider other medical therapies that might target different pathways in this disease process. In addition, we need to define the optimal timing and duration of therapy for this chronic slowly progressive disease; treatments aimed at the early disease process may be ineffective with end-stage tissue changes.

Quantitating aortic regurgitation by cardiovascular magnetic resonance: significant variations due to slice location and breath holding

ObjectivesCompare variability in flow measurements by phase contrast MRI, performed at different locations in the aorta and pulmonary artery (PA) using breath-held (BH) and free-breathing (FB) sequences.MethodsFifty-seven patients with valvular heart disease, confirmed by echocardiography, were scanned using BH technique at 3 locations in the ascending aorta (SOV = sinus of Valsalva, STJ = sinotubular junction, ASC = ascending aorta at level of right pulmonary artery) and 2 locations in PA. Single FB measurement was obtained at STJ for aorta. Obtained metrics (SV = stroke volume, FV = forward volume, BV = backward volume, RF = regurgitant fraction) were evaluated separately for patients with aortic regurgitation (AR, n = 31) and mitral regurgitation (n = 26).ResultsNo difference was noted between the two measurements in the PA. Significant differences were noted in measured SV at different aortic locations. SV measurements obtained at ASC correlated best with the measurements obtained in the PA. Strongest correlation of AR was measured at the STJ.ConclusionMeasurements of flow volumes by phase contrast MRI differ depending on slice location. When using stroke volumes to calculate pulmonary to systemic blood flow ratio (Qp/Qs), ASC should be used. For quantifying aortic regurgitation, measurement should be obtained at STJ.Key Points• Aortic regurgitation can be accurately measured by MRI.• Aortic regurgitation measurement by MRI varies according to the location where measured.• Aortic regurgitation can also be measured by MRI without breath hold.

Not the usual cardiac rhythm device infection: A fastidious pathogen with several teaching points

Because cardiac device infections may include fastidious pathogens, extended incubation of blood cultures is suggested. A patient with an infection of a right ventricular lead implantable cardioverter defibrillator (ICD) system is described. The device was implanted 6 months earlier. The pathogen was identified as Haemophilus parainfluenzae, which was cultured within 72 hours and was presumably from a respiratory tract infection. Extended incubation was not necessary to culture this fastidious pathogen. Two large retrospective studies suggest that prolonged incubation for fastidious organisms is generally not necessary because of advances in culture media and automated blood culture systems.

Quantification of aortic regurgitation and stroke volume by CMR - variation due to slice plane position. It matters where you measure!

Purpose Aortic regurgitation by CMR has been assessed in various locations, including sinus of valsalva (SOV), sinotubular junction (STJ), and ascending aorta (ASC). Variability in obtained measurements and interchangeability of these locations and methods in patients with varying valvular disease severity is unknown. We sought to determine the most appropriate aortic level for accurate phase contrast quantitative (Q) flow measurement of forward and backward flow and calculation of Qp:Qs in patients with valvular heart disease.