Detailed distribution of acute pulmonary thromboemboli: direct evidence for reduction of acquisition length and radiation dose for triple rule-out CT angiography.

PURPOSE: To reduce the redundant acquisition range and total radiation dose for planning appropriate "triple rule-out" CT angiography (CTA) for acute chest pain, we evaluated the detailed distribution of pulmonary thromboemboli (PTE) in subjects with acute PTE. MATERIALS AND METHODS: Retrospective review of CTA n 75-subjects (48-females; 57 ± 16 years) with proven acute PTE was performed to determine whether PTE was present solely above the aortic arch or below the heart. RESULTS: 77% had PTE in the right upper lobe but none had PTE that were solely located higher than the aortic arch; 73% had PTE in the right middle lobe; 80% had PTE in the right lower lobe, but none had PTE that were solely located lower than the heart. 81% had PTE in the left upper lobe and 3% of them had PTE solely located higher than the aortic arch; both had PTE in the right upper, middle, and lower, and the left lower lobes. 75% had PTE in the left lower lobe, but none had PTE that were solely located lower than the heart. The acquisition length in limited CTPA in this population was reduced on average by 21.9% compared with full CTPA. CONCLUSIONS: In subjects with acute PTE, there were none whose PTE was located solely in the upper lobes which were higher than the aortic arch, nor solely in the lower lobes which were lower than the heart. A limited range triple rule-out CTA protocol would decrease effective doses approximately 22% relative to full chest CTA and may help the physician find all PE present.

Attenuated phrenic long-term facilitation in orexin neuron-ablated mice.

We examined phrenic long-term facilitation (LTF) in urethane-anesthetized, vagotomized, paralyzed, and artificially ventilated orexin neuron-ablated mice and their wild-type littermates. Effect of isocapnic single hypoxic episode (SHE, for 45 s) and intermittent hypoxia (IH, 5 times of SHE separated by 5 min) on phrenic nerve activity (PNA) was measured for 1-2h. In wild-type mice, amplitude of PNA gradually increased after cessation of IH and reached 55+/-15% above the baseline (n=7, p<0.05) whereas the burst rate of PNA did not change. Qualitatively similar but significantly attenuated response (16+/-8%) was observed in orexin neuron-ablated mice. SHE did not affect amplitude nor frequency in both animals. We conclude that orexin contributes to eliciting phrenic LTF at least in part in mice. This study also showed, for the first time, phrenic LTF following IH in WT mice. Characteristics of phrenic and ventilatory LTF in mice were similar to those in rats.

[Pulmonary hypertension in a patient on chronic hemodialysis].

A 52-year-old woman with end-stage renal disease and long-term hemodialysis complained of worsening exertional dyspnea. A chest X-ray showed cardiomegaly. She was admitted to our hospital because an echocardiogram suggested pulmonary hypertension. Right heart catheterization revealed pulmonary hypertension, but pulmonary perfusion scintigraphy with Tc-99m-MAA showed no evidence of pulmonary thromboembolism. We gave her a diagnosis of pulmonary arterial hypertension associated with Sjögren syndrome on the basis of a positive serological test (SS-A. SS-B) and the findings of lip biopsy. After four months of therapy with bosentan, her 6-minute walk distance, estimated pulmonary arterial pressure and brain natriuretic peptide (BNP) improved. Bosentan is mainly cleared by hepatic elimination and its dialysis clearance is low. Bosentan for the treatment of pulmonary hypertension was safe as well as effective in this patient with end-stage renal disease and hemodialysis. In consideration of the relationship between pulmonary hypertension and end-stage renal disease, and hemodialysis, bosentan was considered to be a reasonable and effective treatment.

Correlation between plasma brain natriuretic peptide concentration and lung thallium-201 uptake on exercise thallium perfusion images.

The plasma brain natriuretic peptide (BNP) concentration at rest correlates with left ventricular end-diastolic pressure (LVEDP), left ventricular ejection fraction (LVEF), and pulmonary capillary wedge pressure (PCWP). High lung thallium-201 uptake has been reported to be associated with hemodynamic variables such as LVEDP, LVEF, and PCWP. However, there is no study that has investigated the correlation of plasma BNP concentration with lung thallium-201 uptake. We examined whether the plasma BNP concentration was related to lung thallium-201 uptake. Before exercise, venous blood samples were obtained from 39 patients with old myocardial infarction. We investigated the correlations between plasma BNP concentration and lung thallium-201 uptake, and whether they were related to LVEF, extent of nonviable myocardium, and ischemic myocardium, respectively, with thallium-201 exercise stress testing. The plasma BNP concentration significantly correlated with lung thallium-201 uptake (P < 0.05), nonviable segments (P < 0.01), and LVEF (P < 0.01). Lung thallium-201 uptake correlated with nonviable segments (P < 0.01). Our results suggest that increased secretion of BNP is related to increased lung thallium-201 uptake, and they are related to the extent of nonviable myocardium and decreased left ventricular function. Plasma BNP concentration and lung thalium-201 uptake may reflect the extent of myocardial fibrosis causing myocyte stretch.