N-terminal Pro-Brain Natriuretic Peptide and Renal Insufficiency as Predictors of Mortality in Pulmonary Hypertension

BACKGROUND

N-terminal pro-brain natriuretic peptide (NT-proBNP) is a byproduct of the brain natriuretic peptide (BNP) that was shown to be of prognostic value in pulmonary hypertension (PH). The role of NT-proBNP in PH has to be determined, especially under the influence of renal impairment that might lead to an accumulation of the peptide, and may be a sign of increased mortality per se.

METHODS

We assessed NT-proBNP, BNP, renal function, and hemodynamic parameters (during right-heart catheterization) in 118 consecutive patients with isolated PH, excluding left-heart disease. Depending on the calculated creatinine clearance, patients were classified into different groups of renal function. Correlation analysis was performed on all key parameters. Results were then compared between the levels of renal function. The prognostic value of each parameter was assessed during a mean follow-up period of 10 months.

RESULTS

Twenty-two patients (approximately 19%) had significantly impaired renal function (creatinine clearance < 60 mL/min). Although the overall levels of NT-proBNP were correlated with hemodynamics, we observed no correlation in the group with significant renal dysfunction. Moreover, NT-proBNP was related to creatinine clearance. Finally, NT-proBNP and renal insufficiency were independent predictors of death during univariate and multivariate analysis, whereas BNP only predicted mortality in univariate analysis.

CONCLUSIONS

The diagnostic accuracy of NT-proBNP as a parameter of the hemodynamic status is diminished by renal function. However, NT-proBNP could be superior to BNP as a survival parameter in PH because it integrates hemodynamic impairment and renal insufficiency, which serves as a sign of increased mortality per se.

Pulmonary embolism: comprehensive diagnosis by using electron-beam CT for detection of emboli and assessment of pulmonary blood flow

PURPOSE

To comprehensively assess thoracic anatomy and pulmonary microcirculation in pulmonary embolism by using computed tomographic (CT) angiography of the pulmonary arteries combined with functional CT imaging of blood flow.

MATERIALS AND METHODS

Twenty-two patients suspected of having acute pulmonary embolism underwent contrast material-enhanced thin-section electron-beam CT angiography of the pulmonary arteries. In addition, in each patient, a dynamic multisection blood flow CT study was performed on a 7.6-cm lung volume with electrocardiographic gating. Pulmonary blood flow was calculated, and perfusion parameters were visualized on color-coded maps. The color-coded maps and CT angiograms were independently evaluated, segment by segment, by two readers for perfusion deficits and the presence of clots, respectively. The results were compared.

RESULTS

Mean pulmonary blood flow was 0.63 mL/min/mL in the occluded segments versus 2.27 mL/min/mL in the nonoccluded segments (P: =.001). The sensitivity and specificity of perfusion maps for the presence of segmental pulmonary embolism compared with those of CT angiography were 75.4% and 82.3%, respectively, with positive and negative predictive values of 79.6% and 84.7%, respectively. The false-negative findings were caused mainly by partial occlusion of vessels. In eight patients, a substantial alternative or additional pathologic entity was diagnosed.

CONCLUSION

By combining CT angiography and dynamic CT imaging, a comprehensive and noninvasive diagnosis of thoracic structure and function is feasible with a single modality.

Segmental and subsegmental pulmonary arteries: evaluation with electron-beam versus spiral CT

PURPOSE

To compare contrast agent-enhanced spiral and electron-beam computed tomography (CT) for the analysis of segmental and subsegmental pulmonary arteries.

MATERIALS AND METHODS

CT angiography of the pulmonary arteries was performed in 56 patients to rule out pulmonary embolism. Electron-beam CT was performed in 28 patients. The other 28 patients underwent spiral CT with comparable scanning protocols. The depiction of segmental and subsegmental arteries was analyzed by three independent readers. The contrast enhancement in the main pulmonary artery was measured in each patient.

RESULTS

Analysis was performed in 1,120 segmental and 2, 240 subsegmental arteries. One segmental (RA7, P =.010) and two subsegmental (LA7b, P =.029; RA6a+b, P =.038) arteries in paracardiac and basal segments of the lung were depicted significantly better with electron-beam CT. There was no statistically significant difference between electron-beam and spiral CT in the total number of analyzable peripheral arteries depicted. The mean contrast enhancement in the main pulmonary artery was 362 HU in electron-beam CT studies versus 248 HU in spiral CT studies.

CONCLUSION

Detailed visualization of peripheral pulmonary arteries is well within the scope of advanced CT techniques. Electron-beam CT has minor advantages in analyzing paracardiac arteries, probably because of reduction of motion artifacts and higher contrast enhancement. Further studies are needed to establish whether electron-beam CT allows a more confident diagnosis of emboli in these vessels.

Inversion recovery single-shot TurboFLASH for assessment of myocardial infarction at 3 Tesla

PURPOSE

The aim of the study was to assess the diagnostic accuracy of imaging myocardial infarction with a single-shot inversion recovery turbofast low-angle shot (SS IR turboFLASH) sequence at 3.0 Tesla in comparison with an established segmented inversion recovery turboFLASH sequence at 1.5 Tesla.

MATERIALS AND METHODS

Fifteen patients with myocardial infarction were examined at a 1.5 Tesla magnetic resonance (MR) System (Avanto, Siemens, Medical Solutions) and at a 3.0 Tesla MR system (TIM Trio, Siemens, Medical Solutions). Imaging delayed enhancement was started 15 minutes after application of contrast material. A SS IR turboFLASH was performed at 3.0 Tesla and compared with a segmented IR turboFLASH sequence at 1.5 and at 3.0 Tesla. The IR turboFLASH sequence at 1.5 Tesla served as reference method. Infarct volumes, contrast/noise ratio (CNR) of infarcted and normal myocardium were compared with the reference method.

RESULTS

The Single-Shot IR turboFLASH technique allows imaging 9 slices during a single breath-hold. The CNR between infarction and normal myocardium of the reference method was 6.4 at 1.5 Tesla. The mean value of CNR of the IR turboFLASH sequence was 7.3 at 3.0 Tesla for the single-shot technique and 14.1 at 3.0 Tesla for the segmented technique. No significant difference was found for the CNR values of the reference technique at 1.5 Tesla and the single-shot technique at 3.0 Tesla, however for the comparison of the segmented technique at 1.5 and at 3 Tesla (P = 0.0001). The correlation coefficients of the infarct volumes, determined with the Single-Shot IR turboFLASH and the segmented IR turboFLASH technique at 3.0 compared with the reference method, were r = 0.95 (P < 0.0001) and r = 0.95 (P < 0.0001).

CONCLUSION

The loss of CNR, which is caused by replacement of the segmented technique by the single-shot technique, is completely compensated by the approximately 2-fold CNR increase at the higher field strength. The IR turboFLASH technique at 3.0 Tesla IR can be used as a single-shot technique with acquisition of 9 slices during a single breath-hold without loss of diagnostic accuracy compared with the segmented technique at 1.5 Tesla.

MRI of Myocardial Perfusion

An overwhelming number of myocardial perfusion studies are done by nuclear isotope imaging. Magnetic resonance imaging during the first pass of an injected, contrast bolus has some significant advantages for detection of blood flow deficits, namely higher spatial resolution, absence of ionizing radiation, and speed of the test. Previous clinical studies have demonstrated that excellent sensitivity and specificity can be achieved with MR myocardial perfusion imaging for detecting coronary artery disease, and assessment of patients with acute chest pain. Furthermore, an absolute quantification of myocardial blood flow is feasible, as was demonstrated by comparison of MR perfusion imaging, to measurements with isotope labeled microspheres in experimental models. An integrated assessment of perfusion, function, and viability, is thus feasible by MRI to answer important clinical challenges such as the identification of stunned or hibernating, but viable myocardium.

Assessment of collateralized myocardium with Cardiac Magnetic Resonance (CMR): transmural extent of infarction but not angiographic collateral vessel filling determines regional function and perfusion in collateral-dependent myocardium

BACKGROUND

Angiographic collateral vessel filling is limited to evaluate collateral-dependent myocardium. We hypothesize, that quantitative assessment of regional myocardial function, perfusion and viability with Cardiac Magnetic Resonance (CMR) adds complementary information to angiography of collateralized myocardium.

METHODS

CMR was performed in 30 patients with one chronic occluded coronary artery and no further flow limiting stenosis to assess transmural extend of infarction (TEI), resting perfusion and perfusion during adenosine-induced hyperemia and regional wall thickening (RWT) in collateral-dependent and antegradely-perfused myocardium. Collateral vessels were evaluated by angiography and the Rentrop grade (0-3).

RESULTS

In 15 patients with < 50% TEI in collateral-dependent myocardium resting perfusion (1.08+/-0.22 ml/min/g), hyperemia (2.21+/-0.73 ml/min/g) and RWT (4.0+/-2.6 mm) were similar to antegradely-perfused myocardium (rest 1.14+/-0.20 and hyperemia 2.46+/-0.82 ml/min/g, RWT 4.3+/-1.7 mm). In 15 patients with > or = 50% TEI in collateral-dependent myocardium resting perfusion and hyperemia as well as RWT were significantly lower (rest 0.84+/-0.19, p<0.001 and hyperemia 1.34+/-0.43 ml/min/g, p<0.001; RWT 1.0+/-1.0 mm, p<0.0001) compared to antegradely-perfused myocardium. There was an inverse correlation between TEI and resting or hyperemic perfusion or RWT. In contrary, resting perfusion and hyperemia as well as RWT in collateral-dependent myocardium were not different between patients with good (2-3) compared to patients with poor Rentrop grade (0-1). There was no correlation between TEI and Rentrop grade.

CONCLUSION

Function and perfusion in collateral-dependent myocardium are preserved, if transmural extent of infarction is limited (< 50%). This is independent of their angiographic collateral vessel filling. Thus, CMR adds complementary information to angiographic standard assessment of collateral vessels.

Photochemical synthesis of benzoyl spiro[2.2]pentanes

In the present study, we describe the photochemical behaviour of 2-mesyloxy phenyl ketones 8 and 12 bearing a cyclopropane moiety in the side-chain. Irradiation of 8 and 12 leads to the corresponding benzoyl spiro[2.2]pentanes as a consequence of an initial gamma-H-shift, subsequent elimination of MsOH (accompanied by a spin-center shift) and cyclization of the resulting 1,3-diradicals. In contrast, a corresponding phenyl ketone without a mesyloxy group in the 2-position, and thus a potential reactant of the "classical" Norrish-Yang reaction, shows no photochemical reaction. By means of quantum chemical calculations we discovered that in the presence of a mesyloxy group the activation barrier for the photochemical gamma-H-shift is substantially decreased. Furthermore, a photoinduced skeletal rearrangement of benzoyl spiro[2.2]pentane to 2-cyclobutylidene-acetophenone could be observed. Compared to the common methods used to synthesize spiro[2.2]pentanes, the photochemical preparation of benzoyl spiro[2.2]pentane presented herein is the first example where a bond between the spiro atom and an adjacent atom is formed.