Velocity of blood flow in health and disease

Background free in vivo29Si MR imaging with hyperpolarized PEGylated silicon nanoparticles

This study demonstrated the potential of 50 nm PEGylated Si NPs for high-resolution in vivo29Si MR imaging, emphasizing their biocompatibility and water dispersibility. The acquisition of in vivo Si MR images using the lowest reported dose after subcutaneous and intraperitoneal administration opens new avenues for future 29Si MR studies.

Association of pulmonary transit time by cardiac magnetic resonance with heart failure hospitalization in a large prospective cohort with diverse cardiac conditions

BACKGROUND

Longer pulmonary transit time (PTT) is closely associated with hemodynamic abnormalities. However, the implications on heart failure (HF) risk have not been investigated broadly in patients with diverse cardiac conditions. In this study we examined the long-term risk of HF hospitalization associated with longer PTT in a large prospective cohort with a broad spectrum of cardiac conditions.

METHODS

All subjects were prospectively recruited to undergo cardiac magnetic resonance (CMR). The dynamic images of first-pass perfusion were acquired to assess peak-to-peak pulmonary transit time (PTT) which was subsequently normalized to RR interval duration. The risk of HF was examined using Cox proportional hazards models adjusted for baseline confounding risk factors.

RESULTS

Among 506 consecutively consented patients undergoing clinical cardiac MR with diverse cardiac conditions, the mean age was 63 ± 14 years and 373 (73%) were male. After a mean follow up duration of 4.5 ± 3.0 years, 70 (14%) patients developed hospitalized HF and of these 6 died. A normalized PTT ≥ 8.2 was associated with a significantly increased adjusted HF hazard ratio of 3.69 (95% CI 2.02, 6.73). The HF hazard ratio was 1.26 (95% CI 1.18, 1.33) for each 1 unit increase in PTT which was higher among those preserved (1.70, 95% CI 1.20, 2.41) compared to those with reduced left ventricular ejection fraction (< 50%) (1.18, 95% CI 1.09, 1.27). PTT remained a significant risk factor of hospitalized HF after additional adjustment for N-terminal pro-hormone brain natriuretic peptide (NT-proBNP) or left ventricular global longitudinal strain with additionally demonstrated incremental model improvement through likelihood ratio testing.

CONCLUSIONS

Our findings support the role of PTT in assessing HF risk among patients with broad spectrum of cardiac conditions with reduced as well as preserved ejection fraction. Longer PTT duration is an incremental risk factor for HF when baseline global longitudinal strain and NT-proBNP are taken into consideration.

Avaliação de diferentes tempos de trânsito do meio de contraste intravascular em exames de tomografia computadorizada coronariana

Objective

To measure the transit times (TTs) of contrast agents among the injection site (antecubital vein), superior vena cava, pulmonary trunk, and ascending aorta, in coronary computed tomography angiography (CTA) examinations of outpatients with no history of cardiovascular or lung disease, thus defining reference values for those TTs.

Materials and Methods

The contrast TTs from the injection site (antecubital vein) to the superior vena cava, from the superior vena cava to the pulmonary trunk, and from the pulmonary trunk to the ascending aorta were measured by monitoring contrast enhancement in real time (bolus tracking). Cardiac output was measured by the geometric method during the CTA examination and was correlated with the contrast TT.

Results

Forty-three individuals were analyzed. The mean contrast TT was 13.1 s overall (from the antecubital vein to the ascending aorta), 3.0 s from the superior vena cava to the pulmonary trunk, and 7.2 s from the pulmonary trunk to the ascending aorta. There was a tendency toward a correlation between contrast TT and cardiac output (p = 0.055).

Conclusion

The reference values established here for contrast TTs among the superior vena cava, pulmonary trunk, and ascending aorta will serve as a basis for clinical evaluation.

Pulmonary hypertension detection by computed tomography pulmonary transit time in heart failure with reduced ejection fraction

Aims

To evaluate the relationships between pulmonary transit time (PTT), cardiac function, and pulmonary haemodynamics in patients with heart failure with reduced ejection fraction (HFrEF) and to explore how PTT performs in detecting pulmonary hypertension (PH).

Methods and results

In this prospective study, 57 patients with advanced HFrEF [49 men, 51 years ± 8, mean left ventricular (LV) ejection fraction 26% ± 8] underwent echocardiography, right heart catheterization, and cardiac computed tomography (CT). PTT was measured as the time interval between peaks of attenuation in right ventricle (RV) and LV and was compared between patients with or without PH and 15 controls. PTT was significantly longer in HFrEF patients with PH (21 s) than in those without PH (11 s) and controls (8 s) (P &lt; 0.001) but not between patients without PH and controls (P = 0.109). PTT was positively correlated with pulmonary artery wedge pressure (PAWP) (r = 0.74), mean pulmonary artery pressure (r = 0.68), N-terminal pro-B-type natriuretic peptide (r = 0.60), mitral (r = 0.54), and tricuspid (r = 0.37) regurgitation grades, as well as with LV, RV, and left atrial volumes (r from 0.39 to 0.64) (P &lt; 0.01). PTT was negatively correlated with cardiac index (r = −0.63) as well as with LV (r = −0.66) and RV (r = −0.74) ejection fractions. PAWP, cardiac index, mitral regurgitation grade, and RV end-diastolic volume were all independent predictors of PTT. PTT value ≥14 s best-detected PH with 91% sensitivity and 88% specificity (area under the receiver operating characteristic curve: 0.95).

Conclusion

In patients with HFrEF, PTT correlates with cardiac function and pulmonary haemodynamics, is determined by four independent parameters, and performs well in detecting PH.

Left ventricular filling pressure assessment using left atrial transit time by cardiac magnetic resonance imaging

BACKGROUND

Left atrial (LA) size and function reflect left ventricular (LV) hemodynamics. In the present study, we developed a novel method to determine LA circulation transit time (LATT) by MRI and demonstrated its close association with LV filling pressure.

METHODS AND RESULTS

All subjects were prospectively recruited and underwent contrast-enhanced MR dynamic imaging. Mean LATT was determined as the time for contrast to transit through the LA during the first pass. In an invasive study group undergoing clinically indicated cardiac catheterization (n=25), LATT normalized by R-R interval (nLATT) was closely associated with LV early diastolic pressure (r=0.850, P=0.001), LV end-diastolic pressure (r=0.910, P<0.001), and mean diastolic pressure (r=0.912, P<0.001). In a larger noninvasive group (n=56), nLATT was prolonged in patients with LV systolic dysfunction (n=47) (10.1±3.0 versus 6.6±0.7 cardiac cycles in normal control subjects, n=9; P<0.001). Using a linear regression equation derived from the invasive group, noninvasive subjects were divided into 3 subgroups by estimated LV end-diastolic pressure: ≤10 mm Hg, 11 to 14 mm Hg, and ≥15 mm Hg. There were graded increases from low to high LV end-diastolic pressure subgroups in echocardiographic mitral medial E/e' ratio: 9±5, 11±4, and 13±3 (P=0.023); in B-type natriuretic peptide (interquartile range): 44 (60) pg/mL, 87 (359) pg/mL, and 371 (926) pg/mL (P=0.002); and in N-terminal pro-B-type natriuretic peptide: 57 (163) pg/mL, 208 (990) pg/mL, and 931 (1726) pg/mL (P=0.002), demonstrating the ability of nLATT to assess hemodynamic status.

CONCLUSIONS

nLATT by cardiac MR is a promising new parameter of LV filling pressure that may provide graded noninvasive hemodynamic assessment.

Heart Failure: Evaluation of Cardiopulmonary Transit Times with Time-resolved MR Angiography

PURPOSE

To measure cardiopulmonary transit times in patients with heart failure by using low-dose, time-resolved magnetic resonance (MR) angiography and to determine if transit curves reflect conventional MR indexes of cardiac function.

MATERIALS AND METHODS

Twenty-six patients with heart failure and left ventricular (LV) systolic dysfunction (17 men and nine women; age range, 22-78 years) and thirteen control subjects (eight men and five women; age range, 23-59 years) were examined with MR imaging. The examination consisted of rapid cine MR imaging throughout the heart, followed by contrast material-enhanced time-resolved three-dimensional MR angiography of the cardiac chambers and pulmonary vasculature. Time-intensity curves for the pulmonary artery and ascending aorta were derived from the MR angiography images. Cardiopulmonary transit times and dispersions (full widths at half maximum [FWHM]) were determined from the curves. Transit times and FWHM values for the patients with heart failure were compared with control values by using two-tailed t tests, and transit time was correlated with standard LV functional parameters calculated from the cine MR images.

RESULTS

Cardiopulmonary transit times and FWHM values were significantly prolonged in the patients with heart failure compared with those in the control patients (P <.001). Transit time correlated directly with LV end-diastolic and end-systolic volumes and inversely with LV ejection fraction (R > 0.60). However, transit time did not correlate strongly with age, body surface area, heart rate, LV mass, stroke volume, cardiac output, or sphericity index.

CONCLUSION

Time-resolved MR angiography allows determination of cardiopulmonary transit times that are significantly prolonged in heart failure and correlate directly with LV volumes and inversely with LV ejection fraction.

Circulation time end points. A quantitative comparison of saccharin and radioiodinated albumin as indicators

Ideal measurements are both simple and precise. The subjective circulation time has provided more simplicity than precision to three generations of physicians attempting to analyze cardiac function. Other more complex and less available measurements have displaced the circulation time from its prior vogue, probably because of the wide ranges of normal circulation time values. Yet, no other bedside measurement of cardiac function reflects both cardiac output and central blood volume with a single result.

The peripheral arrival characteristics of radioisotope-labeled albumin are described in 15 normal subjects and in 13 patients with heart failure. These circulation-times are compared with the taste end point of the saccharin indicator simultaneously injected.

Taste threshold, a variable not dependent on cardiac status, determines a significant proportion of the circulation time in both normal and failing circulations.

The wide availability of instruments which measure radioactivity, dye density, or thermal change as a function of time could reinvest the circulation time with a new precision, in return for a modest loss of simplicity. Bypass of the noncardiac variable taste threshold may be added to the other well-described advantages of an objective circulation-time measurement by use of the time of half-peak concentration as the end point in recording the circulation time.

Reliability of subjective circulation time determinations: a comparison between objective and subjective methods

When the fully objective dermofluorographic method of measurement of circulation time was compared with the subjective Decholin and saccharin methods, it was found that the values obtained with the subjective methods were often unreliable. The error was unpredictable in magnitude and occurrence, and was maximal in patients with failure.