Prolonged PR interval despite a programmed short sensed AV delay: the role of intra-atrial conduction time.

Intracavitary electrogram (IEGM) is a useful tool in the interpretation of difficult pacemaker electrograms. A case of 320 ms P-V spike interval on the surface ECG despite a 110 ms programmed sensed AV delay is presented. Atrial IEGM revealed atrial tachycardia with a significant atrial conduction delay.

Quantitative measurement of endothelium derived nitric oxide production of the internal mammary artery bypass graft during extracorporeal circulation.

OBJECTIVE: This study was undertaken to determine the extent of endothelium derived nitric oxide (EDNO) production of the internal mammary artery (IMA) bypass graft and of the native coronary circulation by measuring its stable metabolite (NO2: nitrite) in different sampling sites: internal mammary free cut end flow, in the coronary sinus prior and after anastomosis completion, and to compare them to the nitrite level of the normal plasma. METHODS: Nitrite level was determined with fluoroscopy using 4 hydroxycoumarin nitrozation in 50 consecutive patient undergoing onpump myocardial revascularization. RESULTS: Nitrite levels in the normal plasma were found to be 31.2 micromol. Nitrite level in systemic and coronary circulation after total heparinization, prior to extracorporeal circulation (ECC) was found to be 60.8 micromol (lower quartile /l.q./: 46.6 micromol, upper quartile /u.q./: 70.0 micromol,) and 58.3 micromol,(l.q.:47.8 micromol, u.q.:70.0 micromol) respectively, and of the IMA bypass graft free cut end flow was 54.4 micromol,(l.q.:42.0 micromol, u.q.:66.8 micromol) while in the coronary sinus, after completion the IMA anastomosis, it was 45.71 micromol (l.q.: 35.0 micromol, u.q.: 55.0 micromol), (all geometric mean). CONCLUSIONS: Total heparinization enhances EDNO production. Nitrite concentration in the IMA free cut end flow is similar or greater, than that of the native coronary circulation, however, after IMA bypass graft construction significant reduction (P<0.001) could be measured in the coronary sinus.

Complications due to abandoned noninfected pacemaker leads.

Noninfected unwanted pacemaker leads are usually abandoned since the reported complication rate related to them is low. We followed 60 patients with noninfected retained leads, and complication was observed in 12 (20%) of them. Lead migration occurred in 5 patients, skin erosion in 3 patients, venous thrombosis in 2 patients, and muscle stimulation in 2 patients. Management of the complications was a surgical procedure in seven patients, including two cases of open heart surgery, while chronic medical treatment was necessary in the other five patients. The results of this study suggest that complications due to noninfected abandoned leads may not be as rare as it was previously thought and may present a significant morbidity and cost burden. With the lead extraction technique available, the issue of the removal of all unwanted pacemaker leads should be addressed.

[Alteration of nitric oxide production during arterial myocardial revascularization using extracorporeal circulation. Quantitative measurement of EDNO production by the internal mammary artery bypass graft]. / A nitrogén-monoxid (NO) metabolizmusának változása extracorporalis keringésben végzett artériás myocardium-revascularisatio során. Az arteria mammaria interna bypass graft endotheliumából származó anyag (EDNO) kiválasztásának mennyiségi mérése.

Authors measured the concentration of stable metabolite (NO2: nitrite) of EDNO (endothelium derived nitric oxide) in the internal mammary artery (IMA) bypass graft with the help of a previously reported method (measurement of effective blood flow capacity of the IMA graft in the coronary sinus). Nitrite level in the systemic circulation prior to extracorporeal circulation (ECC)--(68.1 +/- 6.7 mumol/l) was measured, as well as nitrite concentration in the coronary circulation before and after construction of the IMA bypass graft (62.1 +/- 4.19 mumol/l and 50.26 +/- 4.0 mumol/l respectively). Furthermore, nitrite level in the IMA graft free cut end flow was also determined (64.3 +/- 5.9 mumol/l). These data compared to the nitrite levels in the normal plasma (48.1 +/- 5.9 mumol/l) were found to be higher (p = 0.1, ns.), possibly due to the enhanced EDNO production induced by total heparinization. The nitrite concentration in the IMA free cut end flow is similar or slightly higher than that of the native coronary circulation, however, after IMA bypass construction a relative reduction could be measured in the coronary sinus. Authors believe, that this may be related to the reduction of basal EDNO production caused by supernormal pO2 (215 +/- 19 mmHg) during ECC.

Progression and multiple events in radiation carcinogenesis of rat skin.

The multistage theory of carcinogenesis specifies that cells progress to cancer through a series of discrete, irreversible genetic alterations, but data on radiation-induced cancer incidence in rat skin suggests that an intermediate repairable alteration may occur. Data are presented on cancer induction in rat skin exposed to the following radiations: 1. an electron beam (LET = 0.34 kev/mu), 2. a neon ion beam (LET = 45 kev/mu) and 3. an argon ion beam (LET = 125 kev/mu). The latter 2 beams were generated by the Bevalac at the Lawrence Berkeley Laboratory, Berkeley, CA. About 6.0 cm2 of skin was irradiated per rat. The rats were observed every 6 weeks for at least 78 weeks and tumors were scored at first occurrence. Several histological types of cancer, including squamous and basal cell carcinomas, were induced. The total cancer yield was fitted by the quadratic equation, and the equation parameters were estimated by linear regression for each type of radiation. Analysis of the DNA from the electron-induced carcinomas indicated that K-ras and/or c-myc oncogenes were activated in all tumors tested. In situ hybridization indicated that the cancers contain subpopulations of cells with differing amounts of c-myc and H-ras amplification. The results are consistent with the idea that ionizing radiation produces stable, carcinogenetically relevant lesions via 2 repairable events at low LET and via a non-repairable, linked event pathway at high LET; either pathway may advance the cell by 1 stage in the multistage model.

Case study in perioperative right heart failure.

Today, we are increasingly aware of the important role the right ventricle plays in maintaining hemodynamic stability. When the right ventricle fails, added stress is placed on the cardiovascular system. This article focuses on patients with perioperative right heart failure and the associated complex nursing care that is needed to manage these patients. Three major nursing diagnoses are reviewed, including decreased cardiac output, impaired gas exchange, and high risk for ineffective family coping.

Regulation of growth and differentiation of a rat hepatoma cell line by the synergistic interactions of hormones and collagenous substrata.

Serum-free, hormonally defined media have been developed for optimal growth of a rat hepatoma cell line. The cells' hormonal requirements for growth are dramatically altered both qualitatively and quantitatively by whether they were plated onto tissue culture plastic or collagenous substrata. On collagenous substrata, the cells required insulin, glucagon, growth hormone, prolactin, and linoleic acid (bound to BSA), and zinc, copper, and selenium. For growth on tissue culture plastic, the cells required the above factors at higher concentrations plus several additional factors: transferrin, hydrocortisone, and triiodothyronine. To ascertain the relative influence of hormones versus substratum on the growth and differentiation of rat hepatoma cells, various parameters of growth and of liver-specific and housekeeping functions were compared in cells grown in serum-free, hormonally supplemented, or serum-supplemented medium and on either tissue culture plastic or type I collagen gels. The substratum was found to be the primary determinant of attachment and survival of the cells. Even in serum-free media, the cells showed attachment and survival efficiencies of 40-50% at low seeding densities and even higher efficiencies at high seeding densities when the cells were plated onto collagenous substrata. However, optimal attachment and survival efficiencies of the cells on collagenous substrata still required either serum or hormonal supplements. On tissue culture plastic, there was no survival of the cells at any seeding density without either serum or hormonal supplements added to the medium. A defined medium designed for cells plated on tissue culture plastic, containing increased levels of hormones plus additional factors over those in the defined medium designed for cells on collagenous substrata, was found to permit attachment and survival of the cells plated into serum-free medium and onto tissue culture plastic. Growth of the cells was influenced by both substrata and hormones. When plated onto collagen gel substrata as compared with tissue culture plastic, the cells required fewer hormones and growth factors in the serum-free, hormone-supplemented media to achieve optimal growth rates. Growth rates of the cells at low and high seeding densities were equivalent in the hormonally and serum-supplemented media as long as comparisons were made on the same substratum and the hormonally supplemented medium used was the one designed for that substratum. For a given medium, either serum or hormonally supplemented, the saturation densities were highest for tissue culture plastic as compared with collagen gels.(ABSTRACT TRUNCATED AT 400 WORDS)

Replication of herpes simplex virus type 1 in macrophages from resistant and susceptible mice.

Studies were carried out to determine whether the in vitro capacity of adherent peritoneal cells to replicate herpes simplex virus type 1 (HSV-1) might correlate with the in vivo susceptibility of mice genetically resistant, moderately susceptible, or very susceptible to HSV-1 infection. Unstimulated and proteose peptone-stimulated monolayers restricted viral replication when infected immediately, but replicated HSV-1 when infected after 3 to 7 days of culture. Macrophages from resistant C57Bl/6 mice restricted HSV-1 replication significantly better than cells from susceptible mice. This function did not segregate with resistance, since macrophages from resistant F1 mice failed to restrict HSV-1 replication. Induction of peritoneal exudate cells with thioglycolate yielded cells capable of replicating HSV-1 when infected immediately after plating and after 4 days of culture.