Differential atrial performance at rest and exercise in athletes: Potential trigger for developing atrial dysfunction?

Highly trained athletes show an increased risk of atrial arrhythmias. Little is known about atrial volumes and function during exercise in this population. Our aim was to analyze atrial size and contractile function during exercise. Fifty endurance athletes with 11 ± 8 h of training per week and 30 sedentary control subjects were included. Echocardiography was performed at baseline and during exercise. Left (LA) and right atrial (RA) size and function were assessed by two‐dimensional echocardiography. Peak negative strain (Sa) during atrial contraction and active atrial emptying volume (AEV) were measured. Athletes and control subjects showed a significant increment of deformation and AEV of both atria with exercise (P < 0.01 vs baseline for LA and RA). Among athletes, a subgroup with significant LA (n = 8)/RA (n = 15) dilatation (≥40 mL/m²) showed a significantly lower increment in AEV with exercise (LA?AEV: 1.4 ± 1.1 mL/m² vs 2.1 ± 0.9 mL/m², P = 0.04; RA?AEV: 0.9 ± 0.8 mL/m² vs 2.3 ± 1.1 mL/m², P < 0.01) and lower increment in deformation vs other athletes (LA?Sa: ?3.2 ± 2.9% vs ?9.5 ± 4.4%, P < 0.01; RA?Sa: ?2.5 ± 3.3% vs. ?9.8 ± 3.3%, P < 0.01). During exercise, active atrial strain increases, but less in athletes compared to controls, but due to larger atrial volumes, they reached similar increases in atrial emptying volume. However, this overall lesser deformation increases from a subgroup with significant atrial dilatation showing impairment in atrial contractile reserve.     

Right ventricular outflow tract obstruction as a confounding factor in the assessment of the impact of pulmonary regurgitation on the right ventricular size and function in patients after repair of tetralogy of Fallot

Purpose:

To compare right ventricular (RV) size and function between patients with combined pulmonary regurgitation (PR) plus RV outflow tract (RVOT) obstruction (RVOTO) and patients with isolated PR.

Materials and Methods:

Consecutive individuals with significant PR (PR fraction ≥20%) after tetralogy of Fallot (TOF) repair who underwent cardiovascular magnetic resonance (CMR) were included. Patients with additional hemodynamic abnormalities (residual ventricular septal defect, extracardiac shunt, and/or more than mild regurgitation at a valve other than the pulmonary valve) were excluded. Significant RVOTO was defined as peak gradient across RVOT ≥30 mmHg.

Results:

Significant differences between patients with combined PR+RVOTO (n = 9) and isolated PR (n = 33) were observed in RV end‐diastolic volume (138.6 ± 25.1 vs. 167.0 ± 34.6 mL/m², P = 0.02, respectively), RV end‐systolic volume (65.0 ± 9.6 vs. 92.7 ± 26.2 mL/m², P = 0.003), and RV ejection fraction (RVEF) (52.8 ± 3.7 vs. 45.0 ± 6.4%, P = 0.001). Both PR and peak RVOT gradient were independent predictors of RV size.

Conclusion:

Patients with combined PR+RVOTO had smaller RV volumes and higher RVEF when compared with patients with isolated PR. The confounding effect of RVOTO on RV size and function needs to be considered in CMR studies evaluating patients after TOF repair. J. Magn. Reson. Imaging 2011;33:1040–1046. © 2011 Wiley‐Liss, Inc.     

Cardiovascular magnetic resonance imaging for accurate sizing of the left atrium: predictability of pulmonary vein isolation success in patients with atrial fibrillation

Purpose

To prospectively determine the most reproducible approach for left‐atrial size assessment using cardiovascular magnetic resonance (CMR) imaging in patients with atrial fibrillation and its value for prediction of pulmonary vein isolation (PVI) treatment success.

Materials and Methods

Eighty patients underwent CMR imaging prior to PVI; the CMR examination included standard cine sequences, a multislice cine sequence in 4‐chamber orientation with full left‐atrial coverage, and a contrast‐enhanced MR angiography of the left atrium. Left‐atrial size was determined as: diameter, area, volume segmented from angiography, and diastolic/systolic volumes from cine imaging (Simpson's rule). All measurements were carried out by two independent observers and repeated by one observer to assess inter‐ and intrareader variability. Treatment success was defined as persisting sinus rhythm after PVI (follow‐up period 12.6 ± 6.6 months).

Results

All left‐atrial measurements showed substantial intrareader agreement. Interreader agreement was substantial for diastolic/systolic left‐atrial volumes only. Calculated bias was found to be minimal (0.1%–4.9%). Predictability of PVI treatment success was best using cine volumetric measurements (cutoff value for diastolic volume, 112 mL) yielding a sensitivity and specificity of 80% and 70%, respectively.

Conclusion

Left‐atrial volumetry based on cine imaging represented the most reproducible approach to determine left‐atrial size. PVI success was predicted best using cine volumetry. J. Magn. Reson. Imaging 2011;33:455–463. © 2011 Wiley‐Liss, Inc.     

Rapid and accurate left ventricular chamber quantification using a novel CMR segmentation algorithm: A clinical validation study

Purpose:

To evaluate the clinical performance of a novel automated left ventricle (LV) segmentation algorithm (LV‐METRIC) that involves no geometric assumptions.

Materials and Methods:

LV‐METRIC and manual tracing (MT) were used independently to quantify LV volumes and LVEF (ejection fraction) for 151 consecutive patients who underwent cine‐CMR (steady‐state free precession). Phase contrast imaging was used to independently measure stroke volume.

Results:

LV‐METRIC was successful in all cases. Mean LVEF was within 1 point of MT (Δ 0.6 ± 2.3%, P < 0.05), with smaller differences among patients with (0.5 ± 2.5%) versus those without (0.9 ± 2.3%; P = 0.01) advanced systolic dysfunction (LVEF ≤ 35% by MT). LV volumes by LV‐METRIC were slightly smaller than MT during end‐diastole (3.9 ± 6.8 mL, P < 0.001) and end‐systole (1.4 ± 5.5 mL, P < 0.01). Mean processing time was 22 ± 13 seconds for LV‐METRIC and 4:59 ± 1:56 minutes for MT (P < 0.001). Processing time correlated with LV blood volume by MT (r = 0.43) and LV‐METRIC (r = 0.55), but slope was 10‐fold steeper for MT (0.02 vs. 0.001), indicating greater proportionate time increases in relation to chamber dilation. Compared to stroke volume by phase contrast, LV‐METRIC yielded smaller differences (0.3 ± 18.3 mL) than MT (2.5 ± 17.2 mL; P < 0.001).

Conclusion:

Among a broad series of consecutive patients undergoing CMR, automated LVEF by LV‐METRIC was within 1 point of MT with processing time reduced 14‐fold. Stroke volume by LV‐METRIC yielded improved agreement with an independent standard of phase contrast imaging. J. Magn. Reson. Imaging 2010;31:845–853. ©2010 Wiley‐Liss, Inc.     

Normal biventricular function,volumes, and mass in children aged 8 to 17 years

Purpose

To assess normal values for biventricular function, volumes, and mass with current cardiovascular magnetic resonance (CMR) imaging sequences in children.

Materials and Methods

Included in the study were 60 healthy children aged 8–17 years. A short axis set of contiguous slices was acquired with CMR imaging employing steady‐state free precession. Biventricular end‐diastolic volume (EDV), end‐systolic volume (ESV), ejection fraction (EF), and mass were determined. Uni‐ and multivariate linear regression analyses were performed to study the interrelation of age, gender, and body surface area (BSA) on biventricular volumes and mass. The coefficient of variation was calculated for intra‐ and interobserver variability.

Results

EF did not differ between boys and girls (mean LV‐EF 69 ± (SD) 5%, mean RV‐EF 65 ± 5%). BSA had good (EDV, mass) and modest (ESV) correlation with biventricular measurements. Gender appeared a significant modifier of these relations, whereas age had no independent contribution. The intra‐ and interobserver coefficient of variation was in the range 2.1%–13.9% for biventricular EDV, ESV, and mass.

Conclusion

This study reveals gender‐specific normative data for biventricular function, volumes, and mass in children age 8–17 years that can be used as reference data in the follow‐up of pediatric cardiac patients. J. Magn. Reson. Imaging 2009;29:552–559. © 2009 Wiley‐Liss, Inc.     

Left ventricular infarct size,peri‐infarct zone,and papillary scar measurements: A comparison of high‐resolution 3D and conventional 2D late gadolinium enhancement cardiac MR

Purpose

To compare higher spatial resolution 3D late gadolinium enhancement (LGE) cardiovascular magnetic resonance (Cardiac MR) with 2D LGE in patients with prior myocardial infarction.

Materials and Methods

Fourteen patients were studied using high spatial resolution 3D LGE (1.3 × 1.3 × 5.0 mm³) and conventional 2D LGE (2 × 2 × 8 mm³) scans. The signal‐to‐noise ratio (SNR) and contrast‐to‐noise ratio (CNR) were measured. Total infarct volume, peri‐infarct volume measured in a limited slab, and papillary muscle scar volume were compared using Bland–Altman analysis. Image quality was graded.

Results

3D LGE had higher scar SNR (P < 0.001), higher myocardial SNR (P = 0.001), higher papillary scar‐blood CNR (P = 0.01), and greater sharpness (P = 0.01). The scar volumes agreed (14.5 ± 8.2 for 2D, vs. 13.2 ± 8.8 for 3D), with bias ± 2 standard deviations (SDs) of 0.5 ± 6.8 mL, P = 0.59 R = 0.91. The peri‐infarct volumes correlated but less strongly than scar (P = 0.40, R = 0.77). For patients with more heterogeneous scar, larger peri‐infarct volumes were measured by 3D (1.9 ± 1.1 mL for 2D vs. 2.4 ± 1.6 mL for 3D, P = 0.15, in the matched region). Papillary scar, present in 6/14 (42%) patients, was more confidently identified on 3D LGE.

Conclusion

Higher spatial resolution 3D LGE provides sharper images and higher SNR, but less myocardial nulling. Scar volumes agree well, with peri‐infarct volumes correlating less well. 3D LGE may be superior in visualization of papillary muscle scar. J. Magn. Reson. Imaging 2009;30:794–800. © 2009 Wiley‐Liss, Inc.     

Single-dose time-resolved contrast enhanced hybrid MR angiography in diagnosis of peripheral arterial disease: compared with digital subtraction angiography

Purpose:

To validate cardiovascular magnetic resonance (CMR) arterial wall volume measurement using whole arterial specimens ex vivo.

Materials and Methods:

Twenty cadaveric carotid arteries (from 10 patients) were fixed in formaldehyde and imaged with a clinical T1‐weighted 2D CMR sequence and, for imaging validation, with a high‐resolution 3D sequence. Histological validation was performed by sectioning the arteries and microscopically determining area and volume.

Results:

Comparison between the clinical 2D CMR sequence and the 3D high‐resolution validation sequence showed equivalent luminal volumes (889 vs. 880 mm³; P = 0.54; R² = 0.99), and slightly higher 2D CMR arterial wall volumes (982 vs. 916 mm³; +7%; P < 0.01; R² = 0.96) and adventitial volumes (1901 vs. 1826 mm³; +4%; P < 0.01; R² = 0.99). Comparison between 2D CMR and microscopy, performed over a similar longitudinal extent of vessel, showed slightly higher 2D CMR volumes for the lumen (354 vs. 308 mm³; +14%; P < 0.01; R² = 0.97), arterial wall (388 vs. 351 mm³; +10%; P < 0.01; R² = 0.97) and total volumes (750 vs. 665 mm³; +12%; P < 0.01; R² = 0.95).

Conclusion:

The accuracy of the clinical 2D CMR vessel wall sequence for measuring carotid lumen, adventitial, and wall volumes is good against ex vivo measurements, with minor overestimation. This study validates carotid arterial wall quantification by CMR for atherosclerosis research. J. Magn. Reson. Imaging 2010;31:935–941. ©2010 Wiley‐Liss, Inc.     

Evaluation of left atrial contraction contribution to left ventricular filling using cardiovascular magnetic resonance

Purpose:

To describe a new method to quantify the left atrial contraction contribution (ACC) to left ventricular (LV) filling using cardiovascular magnetic resonance (CMR).

Materials and Methods:

We assessed 120 normal subjects (50% female) using steady‐state free precession CMR volumetry. Volumes measurements were performed using short axis and rotational long axis views. The percentage of ACC was calculated by dividing the LV filling volume resulting from left atrial (LA) contraction by the LV stroke volume (LVSV).

Results:

The described method was well reproducible. The ACC in normal subjects was 15 ± 5% for ages <40 years, 28 ± 8% for ages 40 to 55 years, and 38 ± 5% for ages >55 years. When adjusted for age, ie, dividing the ACC percentage by age, a value between 0.4 and 0.7 was found to represent the normal range of ACC at any age.

Conclusion:

The study presents a new and accurate CMR volumetric method to quantify ACC to LV filling. ACC ranges from 10%–40%, depending on age. J. Magn. Reson. Imaging 2013;37:860–864. © 2012 Wiley Periodicals, Inc.     

Triceps brachii strength and regional body composition changes after detraining quantified by MRI

Purpose:

To determine the triceps brachii functional adaptation and regional body composition changes after 12 months of detraining.

Materials and Methods:

Seventeen healthy young men (22.2 ± 1.0 y, body mass index 24.9 ± 3.1 kg/m²) were put in the detraining regimen for 12 months after completing a 12‐week exercise protocol on isoacceleration dynamometer (5 times a week, 5 daily series with 10 maximal elbow extensions, 1 min rest between sets). Triceps brachii muscle strength was measured by isoacceleration dynamometry, using identical protocol as during the training. Muscle volumes, subcutaneous adipose tissue (SCAT), and intermuscular adipose tissue (IMAT) at mid‐humerus were assessed by using MRI.

Results:

Long‐term detraining resulted in the significant decrease of 17% and 19% in endurance strength and fatigue rate, respectively. Maximal muscle strength slightly changed, and its 4% decrease was not significant. Triceps brachii volumes of both arms returned to their pretraining values (475.7 ± 54.91 cm³ for right arm, and 483.9 ± 77.5 cm³ for left arm). IMAT depots in upper arm significantly increased by 14% after 12 months of detraining, when compared with baseline values (P < 0.05).

Conclusion:

Long‐term detraining leads to triceps brachii adaptation with endurance strength decrease, volume return to its baseline values, and significant IMAT accumulation. IMAT values after 12 months of detraining exceed baseline, pretraining values, which is significant accumulation as a result of physiologically decreased muscle activity. J. Magn. Reson. Imaging 2011;33:1114–1120. © 2011 Wiley‐Liss, Inc.     

Changes of functional status and volume of triceps brachii measured by magnetic resonance imaging after maximal resistance training

Purpose

To evaluate the effect of 6‐week self‐perceived maximal resistance training on muscle volume utilizing magnetic resonance imaging and maximal, average, and endurance strength of the elbow extensors and to assess the relationship between muscle strength and volume before and after the training.

Materials and Methods

This was a prospective blinded study. A total of 15 healthy untrained men, aged 22.5 ± 3.7 years (mean ± SD), were engaged in elbow extensor training using isoacceleration dynamometry for 6 weeks with a frequency of five sessions per week (five sets of 10 maximal voluntary contractions, 1‐minute rest period between each set). Prior to and after the training, cross‐sectional magnetic resonance images of the upper arm were obtained and muscle volumes were calculated using the truncated cone formula.

Results

Average, maximal, and endurance strength of the upper arm extensors increased significantly by 43%, 15%, and 56%, respectively. The volume of triceps brachii increased in both arms (P < 0.05): right from 456.9 ± 113.8 cm³ to 475.8 ± 100.9 cm³ and left from 444.3 ± 121.9 cm³ to 468.4 ± 110.4 cm³, or 5%. Maximal and average strength correlated significantly with muscle volume before and after the training.

Conclusion

A specific 6‐week resistance training protocol resulted in muscle strength improvement, together with increase in triceps brachii muscle volume, as demonstrated by volumetric imaging. J. Magn. Reson. Imaging 2009;29:671–676. © 2009 Wiley‐Liss, Inc.     

Cardiovascular magnetic resonance imaging assessment of diastolic dysfunction in a population without heart disease: a gender-based study

Objectives

Asymptomatic left ventricular (LV) diastolic dysfunction is increasingly recognised as an important diagnosis. Our goal was to study the prevalence and gender differences in subclinical LV diastolic dysfunction, using cardiovascular magnetic resonance imaging (CMR) at 3 T.

Methods

We prospectively studied 48 volunteers (19 male and 29 female, mean age 49?±?7 years) with no evidence of cardiovascular disease. We used CMR to measure left atrium (LA) and LV volumes, LV peak filling rate and transmitral flow.

Results

The overall prevalence of LV diastolic dysfunction in our cohort varied between 20 % (based on evaluation of LV filing profiles) and 24 % (based on the evaluation of the transmitral flow). The prevalence of diastolic dysfunction was higher in men than in women, independently of the criteria used (P between 0.004 and 0.022). Indexed LV end-diastolic volume, indexed LV stroke volume, indexed LV mass, indexed LA minimum volume and indexed LA maximum volume were significantly greater in men than in women (P?<?0.05). All the subjects had LV ejection fractions within the normal range.

Conclusions

It is clinically feasible to study diastolic flow and LV filling with CMR. CMR detected diastolic dysfunction in asymptomatic men and women.

Key Points

? CMR imaging offers new possibilities in assessing left ventricular diastolic function. ? The prevalence of diastolic dysfunction is higher in men than in women. ? The prevalence of some diastolic dysfunction in a normal population is 24 %.     

Hemodynamic aspects of mitral regurgitation assessed by generalized phase-contrast MRI

Purpose:

To investigate the utility of MRI measurement of left atrial (LA) flow patterns and turbulent kinetic energy (TKE) in patients with clinically significant mitral regurgitation.

Materials and Methods:

Three‐dimensional cine phase‐contrast MRI (PC‐MRI) data were acquired in five patients with posterior mitral leaflet prolapse and two normal volunteers. LA flow patterns were assessed using particle trace visualization. Specifically, vortices were recognized by closed streamlines. LA flow distortion was assessed by estimation of TKE. In addition, the regurgitant volume was measured.

Results:

Four of the mitral regurgitation patients had eccentric regurgitant jets directed toward the septum; one patient had a central jet. The dominant systolic vortex was located in proximity to the regurgitant jet. The LA flow was highly disturbed with elevated values of TKE; peak LA TKE ranged from 13 to 37 mJ and occurred consistently at late systole. The average LA TKE per cardiac cycle was significantly related to the regurgitant volume (TKE = 0.573 + 0.179·RegVol, R² = 0.983).

Conclusion:

MRI permits investigations of atrial flow patterns and TKE in significant mitral regurgitation. The degree of LA flow distortion, as measured by the average LA TKE over one cardiac cycle, appears to reflect the severity of regurgitation. J. Magn. Reson. Imaging 2011;33:582–588. © 2011 Wiley‐Liss, Inc.     

Does the amplatzer septal occluder device alter ventricular contraction pattern? A ventricular motion analysis by MR tagging

Purpose:

To assess by cardiovascular magnetic resonance (CMR) and CMR tagging if the Amplatzer Septal Occluder affects right ventricular (RV) and left ventricular (LV) motion pattern.

Materials and Methods:

Sixteen consecutive patients with significant atrial septal defect (ASD) and nine consecutive patients with persistent foramen ovale (PFO) as controls were studied before and a median of 14 days after defect closure by an Amplatzer occluder. By CMR end‐diastolic (EDV) and end‐systolic (ESV) RV and LV volumes were determined. Aortic and pulmonary artery flow was measured for assessment of left‐to‐right shunt (Qp/Qs). By CMR tagging circumferential strain and radial shortening, maximal rotation and torsion were measured,

Results:

In ASD patients RV‐EDV and RV‐ESV decreased (P < 0.05). LV‐EDV and LV‐ESV increased after ASD closure (P < 0.005). Qp/Qs dropped from 1.8 to 1.0 (P < 0.001). PFO patients showed no ventricular volume change after PFO closure. In ASD patients circumferential strain and radial shortening and maximal rotation of the RV decreased by ASD closure (P < 0.01). In LV only maximal rotation at the base and apex decreased significantly (P < 0.05). Torsion remained constant. In PFO patients no tagging parameter changed after defect closure.

Conclusion:

The Amplatzer occluder itself does not change the ventricular contraction pattern. All volume and myocardial deformation changes were caused by ventricular loading shifts. J. Magn. Reson. Imaging 2012;35:949–956. © 2012 Wiley Periodicals, Inc.     

Evaluation of different magnetic resonance imaging techniques for the assessment of active left atrial emptying

Objectives

There is currently no agreement on the best method of assessing active left atrial (LA) emptying. This study evaluated the relative merits of cine- and velocity encoded (VENC) magnetic resonance imaging (MRI) for the assessment of active LA emptying.

Methods

Total LA emptying volume (TLAEV) and active LA stroke volume (ALASV) were assessed in 107 consecutive patients using cine-MRI and transmitral flow measurements by VENC-MRI. The fraction of active LA emptying (ALAEF) was calculated as the ratio of ALASV to TLAEV. LA and left ventricular (LV) output were calculated by multiplying TLAEV and LV stroke volume by heart rate, respectively.

Results

Intra- and inter-observer variances were significantly larger for cine-MRI than for VENC-MRI measurements of ALASV (24.7?mL² vs. 3.7?mL² and 57.7?mL² vs. 4.2?mL²; P?P?P?P?P?Conclusion VENC-MRI is the more appropriate method of assessing active LA emptying and its use should be favoured.

Key Points

? Cardiac magnetic resonance imaging (MRI) offers new possibilities in assessing atrial emptying. ? Cine-MRI measurements of active LA emptying have lower reproducibility than velocity encoded MRI. ? Cine-MRI overestimates the fraction of active LA emptying compared with VENC-MRI. ? VENC-MRI is the more appropriate method of assessing active LA emptying.     

Left atrial dysfunction in type 2 diabetes mellitus: insights from cardiac MRI

Objectives

The left atrium (LA) modulates left ventricular filling through reservoir, conduit and booster pump functions. Only limited data exist on LA involvement in type 2 diabetes mellitus (DM2). This study sought to assess LA function in asymptomatic DM2 with cardiac MRI. We hypothesized that cardiac MRI can detect LA dysfunction in asymptomatic DM2.

Methods

Forty-five patients with asymptomatic DM2 and 24 normoglycaemic controls were studied. MRI cine imaging was performed to measure LA maximal and minimal volumes. A flow-sensitive phase-contrast gradient-echo sequence was used for flow measurements perpendicular to the orifice of the mitral valve, to quantify active LA stroke volume. LA total, passive and active emptying volumes and fractions were calculated.

Results

LA reservoir function, namely LA total ejection fraction, was significantly greater in controls compared to patients with DM2 (62.2?±?5.2 vs 57.0?±?7.6 %, P?=?0.004). LA passive ejection fraction was also greater in the controls (26.2?±?9.5 vs 16.1?±?11.0 %, P?Conclusions Cardiac MRI enables the detection of LA dysfunction in asymptomatic DM2, characterized by a reduction in LA reservoir and conduit functions.

Key Points

? Evaluation of left atrial function is feasible with cardiac MRI ? Type 2 diabetes mellitus is associated with left atrial dysfunction ? Left atrial function modulates left ventricular filling     

Isometric handgrip exercise during cardiovascular magnetic resonance imaging: Set‐up and cardiovascular effects

Purpose:

To establish a suitable setup for combining isometric handgrip exercise with cardiovascular magnetic resonance (CMR) imaging and to assess cardiovascular effects.

Materials and Methods:

Fifty‐three healthy volunteers (31 males, mean age 45 ± 17 years) underwent handgrip exercise in a 3T scanner using a prototype handgrip system and a custom‐made feedback system that displayed the force. Handgrip was sustained at 30% of the maximal contraction for 6–8 minutes. Heart rate, blood pressure (BP), and double product were determined sequentially. Stroke volume was quantified in a subgroup (n = 21) at rest and stress using phase contrast acquisitions.

Results:

Heart rate increased significantly between rest and stress by 20 ± 13%, systolic / diastolic / mean BP by 15 ± 11% / 20 ± 18% / 17 ± 13%, double product by 37 ± 21%, and cardiac output by 27 ± 16% (each P < 0.001). Stroke volume did not significantly increase (3 ± 9%; P = 0.215). Higher age was associated with reduced increase of stroke volume (P = 0.022) and cardiac output (P < 0.001). Overweight subjects showed less increases in heart rate (P = 0.021) and cardiac output (P = 0.002).

Conclusion:

The handgrip exercise during CMR with the presented set‐up leads to considerable hemodynamic changes in healthy volunteers. J. Magn. Reson. Imaging 2013;37:1342–1350. © 2013 Wiley Periodicals, Inc.     

Cardiac magnetic resonance before and after percutaneous pulmonary valve implantation

Purpose

To measure the magnetic resonance (MR) artefact produced by a percutaneous pulmonary valve stent and to evaluate the changes in volumetric and functional right ventricle (RV) parameters due to percutaneous pulmonary valve implantation (PPVI).

Materials and methods

A Melody valve was studied in vitro using clinical cardiac MR (CMR) sequences. In vivo, we analysed the CMR examinations obtained before and after PPVI of 27 consecutive patients. The echocardiography pressure gradient (PG) and catheter PG were measured. The Wilcoxon test was used for comparisons.

Results

In vitro, the least difference between artefact extent and actual valve size (0.1 mm) was obtained with a steady-state free precession (SSFP) sequence. In vivo, RV end-diastolic volume (ml/m²), end-systolic volume (ml/m²) and ejection fraction (%) were 79 ± 42, 43 ± 41 and 49 ± 13 before PPVI and 64 ± 21 (p = 0.054), 30 ± 14 (p = 0.021), and 54 ± 12 (p = 0.018) 6 months after PPVI, respectively. The PG and regurgitation fraction (RF) were 36 ± 15 mmHg and 14 ± 18 % before PPVI and 13 ± 15 mmHg (p < 0.001) and 2 ± 5 % (p = 0.013) after PPVI, respectively. No significant differences were found comparing the PG measured with CMR, echocardiography and catheter.

Conclusions

We showed in vitro that the SSFP sequence produced the most accurate valve measurement. After PPVI, CMR showed a strong decrease of PG and RF with a significant improvement of RV function.     

Measurement and comparison of T1 relaxation times in native and transplanted kidney cortex and medulla

Purpose:

To measure and compare cortical and medullary T1 values in native and transplanted kidneys with a wide range of function as measured by estimated glomerular filtration rate (eGFR).

Materials and Methods:

A total of 27 subjects (12 native and 15 transplants) were studied. Two magnetic resonance imaging (MRI) exams of T1 measurement were performed on separate days for reproducibility study. Group‐wise comparisons of renal T1 on day 1 were performed between subjects with native and transplanted kidneys and also between subjects based on an eGFR threshold of 60 mL/min/1.73m².

Results:

Transplanted kidneys had higher cortical renal T1 (1183 ± 136 msec) than native kidneys (1057 ± 94 msec) with similar results in the medulla. Subjects with an eGFR < 60 mL/min/1.73m² had higher renal T1 than subjects with an eGFR > 60 mL/min/1.73m² (cortical T1: P < 0.0001; medullary T1: P = 0.008). Renal T1 was highly reproducible for both native and transplant groups (with percent differences less than 10%).

Conclusion:

There are differences in cortical and medullary T1 between native and transplanted kidneys at different levels of function. J. Magn. Reson. Imaging 2011;33:1241–1247. © 2011 Wiley‐Liss, Inc.     

Measurement of left atrial volume by 2D and 3D non-contrast computed tomography compared with cardiac magnetic resonance imaging

BackgroundCardiac magnetic resonance imaging (MRI) is considered the gold standard for assessment of left atrial (LA) volume. We assessed the feasibility of evaluating LA volume using 3D non-contrast computed tomography (NCCT). Furthermore, since manual tracing of LA volume is time consuming, we evaluated the accuracy of the LA area using 2D NCCT imaging for LA volume assessment.MethodsMRI and NCCT imaging were performed in 69 patients before and one year after aortic valve replacement. In 3D MRI and 3D NCCT, each slice was manually traced, excluding the pulmonary veins and atrial appendage, and multiplied by slice spacing, thus generating a measure of LA volume. The LA volume was indexed to body surface area. On 2D NCCT, the largest axial cross-section LA area was traced manually.ResultsThe mean LA volume was 102 ± 28 ml in MRI compared with 103 ± 28 ml in 3D NCCT. 3D NCCT showed good agreement with MRI measurements (mean difference −0.7 ml/m²; 95% confidence interval (CI) −2.2 to 0.9). By Bland-Altman, 3D NCCT also showed good agreement with MRI (limits of agreement: −18.7–17.4 ml/m²). Furthermore, good correlation was found between 2D NCCT and 3D NCCT LA volume (r = 0.93).Conclusion2D and 3D measurements of LA volume in non-contrast computed tomography are feasible and accurate.     

Cardiovascular MR dobutamine stress in adult tetralogy of Fallot: disparity between CMR volumetry and flow for cardiovascular function

Purpose:

To evaluate the MR agreement of cardiac function parameters between volumetric (cine SSFP) and phase contrast flow (PC‐flow) assessment in patients with repaired tetralogy of Fallot (r‐TOF) and chronic pulmonary regurgitation (PR) at rest and under dobutamine stress (DS‐MR).

Materials and Methods:

We studied 18 patients with r‐TOF and severe chronic PR (34 ± 12.7 years, PR fraction_[flow] 44 ± 15%) by cardiac MR at rest, 10 and 20 μg/kg/min of dobutamine. We compared analogous functional parameters by volumetry and PC‐flow: (i) Systemic output [left ventricle stroke volume (LV_SV) versus aortic forward flow (AO_FF)], (ii) Pulmonary output [right ventricle stroke volume (RV_SV) versus pulmonary forward flow (PA_FF)], (iii) PR volume [(RV_SV‐LV_SV) versus pulmonary backward flow (PA_BF)], (iv) PR fraction [(RV_SV‐LV_SV/RV_SV) versus (PA_BF/PA_FF)].

Results:

We found excellent Bland‐Altman agreement (mean difference ± limits of agreement, mL/beat/m²) at rest for both the systemic (?0.8 ± 5.7) and pulmonary strokes volumes (?0.1 ± 7.6), which slightly deteriorates during DS‐MR. The PR volume showed acceptable agreement at rest (?3.6 ± 15.1), but also further deteriorated during stress (5.4 ± 24). In contrast, the PR fraction showed poor agreement equally at rest (?5.6 ± 22.8) and DS‐MR (3.2 ± 19.2).

Conclusion:

In r‐TOF with chronic PR, analogous functional parameters should not be used interchangeably between volumetric and PC‐flow assessment during DS‐MR evaluation. J. Magn. Reson. Imaging 2011;33:1341–1350. © 2011 Wiley‐Liss, Inc.