Basic mechanism of atrial and ventricular arrhythmia suppression by heavy ion irradiation in hypercholesterolemic elderly rabbits

Background

Recent development of electrophysiology-guided noninvasive cardiac radioablation therapy for ventricular tachycardia attracts a great deal of attention as a novel antiarrhythmic strategy (Robinson CG, Circulation 2019). As to underlying mechanisms, however, much remains to be clarified. We reported before that a single targeted heavy ion irradiation (THIR 15Gy) to rabbit hearts increased connexin43 (Cx43) expression, and a reduction of vulnerability to ventricular arrhythmias after myocardial infarction.

Purpose

We investigated the effects of THIR on in-vivo cardiac electrophysiology and vulnerability to atrial and ventricular tachyarrhythmias in aged rabbits with hypercholesterolemia.

Methods

Sixteen three-year old rabbits were fed with high fat/cholesterol chow (0.5% cholesterol and 10% coconut oil) for 14 weeks. A single THIR 15Gy was applied to 8 rabbits (HC+THIR) with a heavy ion medical accelerator. Eight rabbits without THIR were used as control (HC).

Results

Serum cholesterol levels in the HC and HC+THIR were 1545+386 and 1569+328 mg/dl (n=8, NS). Atrial (P-wave) late potential in signal-averaged ECG in HC+THIR showed a significantly larger root mean square voltage (RMS) than those in HC (12+0.5 vs. 2+0.5μV, n=4, p<0.01). Ventricular late potentials in HC+THIR showed significantly less fQRS-D than HC (81+5 vs. 89+7 ms); less LAS40 (21+7 vs. 30+4 ms), and larger RMS (99+27 vs. 44+13μV) (n=4, p<0.04). Atrial tachycardia or fibrillation (AT/AF) was induced spontaneously or by programmed/burst pacing of the left atria (LA) in 4 out of 4 HC, whereas in only 1 out of 4 HC+THIR. Ventricular tachycardia or fibrillation (VT/VF) was induced spontaneously or by programmed pacing or left stellate stimulation in 4 out of 4 HC rabbits, whereas in only 1 out of 4 HC+THIR. Immunolabeled Cx40 densities in LA and RA tissue from HC+THIR rabbits were significantly higher than those from HC rabbits by 44% and 60%, respectively (n=4, p<0.01). Comparable upregulation of immunoreactive Cx43 was observed in LV and RV tissue from HC+THIR rabbits. Sympathetic nerve densities in LA, RA, LV and RV tissues, which was labeled with anti-neuronal growth-associated protein 43 (GAP43) antibody and tyrosine hydroxylase (TH) antibody were both significantly less in HC+THIR than those in HC.

Conclusion

These results suggest that THIR may improve cardiac conductivity of HC rabbits in favor of reduction of vulnerability to atrial and ventricular tachycardia/fibrillation, and that this antiarrhythmic effect is attributed to upregulation of gap junction protein (Cx40 and Cx43) and in part to prevention of sympathetic nerve sprouting.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): KAKENHI KIBAN (C) 53020

FDG PET in the evaluation of the aggressiveness of pulmonary adenocarcinoma: correlation with histopathological features

2-[Fluorine-18]fluoro-2-deoxy-d-glucose (FDG) uptake within the primary lesion correlates with survival on positron emission tomography (PET) studies of patients with non-small cell lung cancer. The more metabolically active the tumour, the worse the outcome. The aim of this study was to determine whether a correlation exists between aggressiveness as determined by pathology and the findings of FDG PET in pulmonary adenocarcinoma. Thirty-five patients with 38 adenocarcinomas of the lung were studied. All patients underwent thoracotomy within 4 weeks of the FDG PET study. For semiquantitative analysis, standardized uptake values (SUVs) were calculated. Patients were classified into high SUV (> or = 4.0) and low SUV (<4.0) groups. The degree of FDG uptake (SUVs) in primary lung lesions was correlated with the histopathological features of aggressiveness (pleural involvement, vascular invasion or lymphatic permeation). The mean SUV of aggressive adenocarcinomas (4.36+/-1.94, n = 22) was higher than that of non-aggressive ones (1.53+/-0.88, n = 16) (P < 0.0001). Tumours with a high FDG uptake have a significantly higher likelihood of aggressiveness than those with a low FDG uptake (P = 0.0004). Analysis by the Kaplan-Meier methods revealed that the groups had different prognoses (log-rank test, P = 0.0099). The high SUV group had a significantly worse prognosis. In conclusion, a correlation was seen between aggressiveness as determined by pathology and glucose metabolism as measured by FDG PET in adenocarcinoma of the lung. FDG PET may be used as a non-invasive diagnostic technique in measuring aggressiveness and prognosis in patients with pulmonary adenocarcinoma.

Ongoing prospective study of segmentectomy for small lung tumors. Study Group of Extended Segmentectomy for Small Lung Tumor

BACKGROUND

Lesser resection for small lung tumors remains an unresolved problem. This study was conducted to see whether this type of operation is acceptable or not.

METHODS

From 1992 to 1994, 55 patients were enrolled in a multicenter trial of limited surgical resection for peripheral tumors of less than 2 cm diameter. The procedure consisted of segmentectomy with exploration of lymph nodes by examining frozen sections. The operation was modified if the report was positive. The intersegmental plane was identified by keeping the resected segments inflated and the preserved segments collapsed. To divide the plane, stapling or electrocauterization on the edge of the collapsed area was used. In this way the resection line was delivered beyond the burdened segment; this was called extended segmentectomy.

RESULTS

There were no perioperative deaths, but there were eight postoperative deaths. In 1 patient who died because of local recurrence, it had been known that the margin to the lesion had been narrow (15 mm); 1 had bilateral intrapulmonary nodules, 1 had nodules in the side that was not operated on, and another succumbed to a second neoplasm of small cell lung cancer 4 years after the first operation. The remaining 4 died of nonpulmonary diseases. Almost all other patients are alive and free from recurrence, except for 1 in whom N2 disease was not detected intraoperatively but was confirmed after the operation.

CONCLUSIONS

The interim results suggest that extended segmentectomy is applicable in patients with a small peripheral lung cancer. However, a wide margin and aggressive intraoperative pathologic examinations are mandatory.

[Echo-planar FLAIR imaging in patients with brain disorders: comparative studies with turbo-SE T2WI and turbo-FLAIR]

Fluid-attenuated inversion-recovery (FLAIR) imaging is a technique that produces heavily T2-weighted CSF-nulled images by coupling an inversion pulse followed by long inversion time (TI) to a long echo time (TE) readout. With nulling of the CSF, a tissue abnormality usually becomes the brightest object in the image, thereby improving lesion detection in the brain. The FLAIR technique is also easily adapted to echo-planar imaging (EPI), the most rapid MR imaging technique available. We examined EPI-FLAIR imaging in patients with brain disorders and compared the results with those of turbo-FLAIR and turbo SE T2-weighted imaging. MR imaging was performed on a 1.5 T imager in 29 patients with cerebral infarction and 2 patients with multiple sclerosis. The turbo-SE T2-weighted sequence parameters used were: TR/TE = 4000 ms/99 ms, total scan time = 2 min 12 sec. Turbo-FLAIR sequence parameters were TR/TE/TI = 9000 ms/119 ms/2200 ms, total scan time = 4 min 3 sec. EPI-FLAIR sequence parameters were TE/TI = 60 ms/2200 ms, total scan time = 4.38 sec. EPI-FLAIR images were compared quantitatively and qualitatively with both turbo-FLAIR and turbo-SE T2-weighted images. In the quantiative comparisons of EPI-FLAIR images with turbo-FLAIR and turbo-SE T2-weighted images, lesion-to-white matter contrast and the C/N ratio of EPI-FLAIR images were found to be significantly inferior to both turbo-FLAIR and turbo-SE T2-weighted images (P < 0.001). In the qualitative comparisons, the lesion detection and conspicuty of EPI-FLAIR images were inferior to those of turbo-FLAIR and turbo-SE T2-weighted images. In conclusion, the image quality of EPI-FLAIR images was inferior to that of both turbo-FLAIR and turbo SE T2-weighted images. EPI-FLAIR should not replace turbo-FLAIR.

[Advanced gastric carcinoma with extensive lymph node metastases successfully treated by sequential methotrexate/5-fluorouracil therapy]

A 62-year-old man having advanced gastric carcinoma with extended lymph node metastases was successfully treated by a palliative gastrectomy and 6 courses of sequential methotrexate/5-fluorouracil therapy. No side effects were observed, and all enlarged abdominal lymph nodes disappeared. The complete response has continued for 11 months after the initial treatment.

[Management of airway obstruction using the neodymium-yttrium-aluminium-garnet laser]

The neodymium-yttrium-aluminium-garnet laser (Nd-YAG laser) has proved to be useful therapeutic tool for the management of endobronchial lesions. Between February 1983 and January 1991, 16 patients received endobronchial laser therapy at the Nagasaki University Hospital, 7 patients for tracheal stenosis, and 9 for endobronchial obstruction. In 4 patients with tracheal stenosis, the therapy was performed in an emergency. The type of lesions were lung cancer in 7 patients, thyroid cancer in 3, tracheal tumor (squamous cell carcinoma, and chondrosarcoma) in 2, esophageal cancer in 1, bronchial submucosal tumor in 1, and tracheobronchial tuberculosis in 2. Good symptomatic relief was obtained in 13 patients. One patient died from massive bleeding in the left main stem bronchus. Reobstruction had occurred in 2 patients with cicatricial lesion in right main stem bronchus. In patients with an unresectable malignant lesion, concurrent radiotherapy was needed to prevent the reobstruction.

[Problems of the surgery of the trachea and bronchus and establishment of their safety]

Advances in bronchoplastic surgery have been made in accordance with improvement of suture material and procedures of intraoperative respiratory support. However, further advances in this field should be achieved by lessening the postoperative complications by device to improve blood circulation at anastomosis and by development of ideal artificial tracheal grafts.

[A clinicopathological study of mediastinal tumors]

One hundred and fifty-eight cases of mediastinal tumors have been studied clinicopathologically, based on patients of Nagasaki University Hospital from 1961 to 1984. Of these tumors, 29.7% were thymic tumors, 23.4% neurogenic tumors, and 21.5% were germ cell tumors, the frequencies of which reflected the same tendency as other such reports in Japan. Thirty-three cases were malignant tumors. Among them, thymomas were the most common (48.5%) as Wada et al. have reported. Extrathoracic metastases have observed in 2 thymomas. Thymomas associated with myasthenia gravis were seen in 6 cases in which 5 patients are still alive.