Obstructive sleep apnea and temporal changes in cardiac repolarization in patients undergoing coronary artery bypass grafting

STUDY OBJECTIVES

In coronary artery bypass grafting (CABG), abnormal cardiac repolarization is associated with adverse cardiovascular events that can be measured via the QTc interval. We investigated the impact of obstructive sleep apnea on the change in repolarization after CABG and the association of change in repolarization with the occurrence of major adverse cardiac and cerebrovascular events.

METHODS

A total of 1,007 patients from 4 hospitals underwent an overnight sleep study prior to a nonemergent CABG. Electrocardiograms of 954 patients (median age: 62 years; male: 86%; mean follow-up: 2.1 years) were acquired prospectively within 48 hours before CABG (T1) and within 24 hours after CABG (T2). QTc intervals were measured using the BRAVO algorithm by Analyzing Medical Parameters for Solutions LLC. The change in T2 from T1 for QTc (ΔQTc) was derived, and Cox regression was performed.

RESULTS

Compared with those without, patients who developed major adverse cardiac and cerebrovascular events (n = 115) were older and had (1) a higher prevalence of smoking, hypertension, diabetes mellitus, and chronic kidney disease; (2) a higher apnea-hypopnea index and oxygen desaturation index; and (3) a smaller ΔQTc. Cox regression analysis demonstrated a smaller ΔQTc to be an independent risk factor for major adverse cardiac and cerebrovascular events (hazard ratio: 0.997; P = .032). In the multivariable regression model, a higher oxygen desaturation index was independently associated with a smaller ΔQTc (correlation coefficient: -0.58; P < .001).

CONCLUSIONS

A higher preoperative oxygen desaturation index was an independent predictor of a smaller ΔQTc. ΔQTc within 24 hours after CABG could be a novel predictor of occurrence of major adverse cardiac and cerebrovascular events at medium-term follow-up.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov; Name: Undiagnosed Sleep Apnea and Bypass OperaTion (SABOT); URL: https://classic.clinicaltrials.gov/ct2/show/NCT02701504; Identifier: NCT02701504.

CITATION

Teo YH, Yong CL, Ou YH, et al. Obstructive sleep apnea and temporal changes in cardiac repolarization in patients undergoing coronary artery bypass grafting. J Clin Sleep Med. 2024;20(1):49-55.

Sleep apnea and temporal changes in cardiac repolarization in patients undergoing coronary artery bypass grafting

Background

In coronary artery bypass grafting (CABG), despite re-establishing coronary reperfusion, myocardial recovery and restoration of contractility often occur later, and the risk of adverse cardiovascular events persists during the post-CABG period. The occurrence of adverse cardiovascular events is linked to abnorm-al cardiac repolarisation that can be measured by surface electrocardiograms (ECGs). Sleep apnoea is an emerging cardiovascular risk factor. The relationship between sleep apnoea, abnorm-al cardiac repolarisation, and the occurrence of adverse cardiovascular events is not well studied.

Purpose

We investigated the impact of sleep apnoea on the change in repolarisation after CABG, and if the change in repolarisation is associated with the occurrence of major adverse cardiac and cerebrovascular events (MACCE).

Methods

Between November 2013 and December 2018, 1007 patients from 4 hospitals underwent an overnight sleep study prior to a non-emergent CABG. ECGs were acquired prospectively within 48h before the CABG (T1), and within 24h after the CABG (T2). QTc intervals were measured in three consecutive heart beats in one lead - the preferential lead measurements were lead II, followed by lead V5. QTc intervals were measured using the BRAVO algorithm by Analysing Medical Parameters for Solutions (AMPS) LLC. The change of T2 from T1 for QTc (ΔQTc) was derived. The mean follow-up duration was 2.1 years. MACCE was a composite of cardiovascular death, myocardial infarction, stroke, and unplanned revascularisation.

Results

A total of 954 patients (median age: 62 years; male: 86%) survived the initial 24 hours and had quality ECGs for analysis. Lead II and V5 were measured in 72% and 25% of the cohort, respectively. A total of 115 patients developed MACCE (MACCE group). Compared with the non-MACCE group, the MACCE group was older, had (a) a higher prevalence of smoking, hypertension, diabetes mellitus, and chronic kidney disease, (b) higher apnoea-hypopnoea index (AHI) and oxygen desaturation index (ODI), and (c) a smaller ΔQTc (Table). In Cox regression analysis, a smaller ΔQTc was independently associated with occurrence of MACCE (HR: 1.003; 95% CI: 1.000–1.006; p=0.032).

Older age, history of previous stroke, chronic kidney disease, more severe sleep apnoea (higher AHI, ODI, and severe oxygen desaturation) were associated with smaller ΔQTc. After adjusting for the effects of confounding variables, a higher ODI was independently associated with a smaller ΔQTc (correlation coefficient: −0.58; p&lt;0.001).

Conclusions

In patients undergoing a non-emergent CABG, a smaller ΔQTc during the first 24 hours after the CABG is associated with a higher incidence of MACCE. A higher pre-operative ODI based on a sleep study is an independent predictor of a smaller ΔQTc. This suggests that change in QTc within 24 hours after CABG could be due to sleep apnoea, and it is a novel predictor of occurrence of MACCE at medium term follow-up.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Transition Award and Clinician Scientist Award from the National Medical Research Council of Singapore (award numbers: NMRC/TA/012/2012; NMRC/CSA-INV/002/2015)

A quantitative structure-activity relationship approach for assessing toxicity of mixture of organic compounds

Four types of reactivity indices were employed to construct quantitative structure-activity relationships for the assessment of toxicity of organic chemical mixtures. Results of analysis indicated that the maximum positive charge of the hydrogen atom and the inverse of the apolar surface area are the most important descriptors for the toxicity of mixture of benzene and its derivatives to Vibrio fischeri. The toxicity of mixture of aromatic compounds to green alga Scenedesmus obliquus is mainly affected by the electron flow and electrostatic interactions. The electron-acceptance chemical potential and the maximum positive charge of the hydrogen atom are found to be the most important descriptors for the joint toxicity of aromatic compounds.

First Report of Anthracnose of Malva sylvestris Caused by Colletotrichum trifolii in China

Common mallow (Malva sylvestris L.) is a perennial medicinal plant in the Malvaceae family, which is native to Asia, Europe, and North Africa. In July 2012, typical symptoms of anthracnose disease, with a disease incidence of ~70%, were observed on common mallow in the Medicinal Herb Garden of Shenyang Pharmaceutical University, Liaoning, China. The fungus mainly infected the stalks and leaves of M. sylvestris. Pinpoint, brownish lesions initially appeared at the flowering stage and the disease spread within the field. The lesions on stems gradually enlarged and became dark brown, elliptical, and slightly concave. Concurrently, acervuli and mucilaginous conidial masses of the pathogen appeared on lesions under moist conditions. Conidia were hyaline, one-celled, cylindrical with both ends rounded, and measured 10.0 to 12.5 × 2.5 to 4.0 μm (mean 11.3 × 3.3 μm). The fungus was isolated from symptomatic tissues. Small pieces from leaves and stems were surface disinfested with 70% ethanol and 1.5% sodium hypochlorite for 1 min, then rinsed three times with sterile distilled water, and cultured on potato dextrose agar (PDA) at 25°C. The colonies on PDA had initially white aerial mycelia, and later became greenish black with regularly whorled rings. To confirm Koch's postulates, five 3-month-old plants of M. sylvestris were inoculated with a conidial suspension (10⁵ conidia/ml) prepared from PDA cultures incubated for 14 days. Five non-inoculated plants served as controls. The plants were maintained in the greenhouse at 22 to 25°C and about 75% relative humidity under natural daylight. Typical symptoms on inoculated plants were reproduced after ~10 to 14 days, whereas control plants remained asymptomatic. The pathogen was successfully recovered from symptomatic tissues and re-identified, completing Koch's postulates. The internal transcribed spacer (ITS) and large subunit -28S (LSU) region of rDNA was amplified with primers ITS1/ITS4 and NL1/NL4, respectively, and sequenced. Phylogenetic trees (ITS and LSU) that were obtained using MEGE3.1 with the neighbor-joining method showed that both of the isolates fall in the Colletotrichum trifolii clade. The representative sequences (ITS and LSU) were deposited in GenBank (Accession Nos. KJ155692 and KJ920935). The fungus isolated from symptomatic tissues was identified as C. trifolii on the basis of morphological, cultural characteristics, and sequence analysis (2). According to previous references, C. orbiculare and C. malvarum on Malvaceae were respectively described in America and Europe (1,3,4). However, the isolate from M. sylvestris significantly differed from those of C. orbiculare and C. malvarum in cultural characteristics and sequence analysis. In this paper, the results showed that M. sylvestris is a new host of C. trifolii. To our knowledge, this is the first report of mallow anthracnose caused by C. trifolii in China. References: (1) J. A. Bailey et al. Phytopathology 86:1076, 1996. (2) U. Damm et al. Fungal Divers. 61:29, 2013. (3) K. Hyde et al. Fungal Divers. 39:147, 2009. (4) L. Tosi et al. Plant Dis. 88:425, 2004.

Sensitization of a tumor, but not normal tissue, to the cytotoxic effect of ionizing radiation using Panax notoginseng extract

The aim of the present study was to investigate any sensitization effect of the Panax notoginseng extract (PNE) and the purified Saponin (Rb1) on the radiation response of an experimental tumor (KHT sarcoma) in mice, in comparison with any effects on a normal tissue (bone marrow). PNE at a concentration of 0.1-100 mg/kg produced an increase in tumor radiosensitivity. The sensitization effect was maximal at 10 mg/kg and at 30 minutes after injection. Higher doses were toxic to the bone marrow stem cells. Similarly Rb1 at a concentration 0.001 to 1 mg/kg also produced an increase in tumor radiosensitivity, with maximum effect at 1 mg/kg. Higher doses were not toxic to the bone marrow stem cells in this case. Radiosensitization factors were calculated as ratios of D0 (the radiosensitivity parameter), and these were highly significant for the tumor and very similar for both compounds at the doses used, namely 1.18-1.19. There was no significant effect for bone marrow stem cells (sensitization factors of 0.99 +/- 0.01 for both compounds). The differential effect on tumor, and the magnitude of the radiosensitization, suggest that further purified or synthetic versions of this extract may be useful not only in vascular-related diseases but also in cancer therapy.

Efficacy of Re-188-labelled sulphur colloid on prolongation of survival time in melanoma-bearing animals

In this study, the effectiveness of a 188Re labeled sulfur colloid with two particle size ranges was used to evaluate the effectiveness of this agent on melanoma tumors in mice in terms of animal lifespan.

METHODS

Two separate group of animals were used for investigating biodistribution and survival time. A total of 188 B16F10-melanoma-bearing BDF(1) mice were injected intraperitoneally with 3.7 MBq (0.1mCi)/2mL of radiolabeled sulfur colloid ten days after intraperitoneal inoculation of 5x10(5) B16F10 melanoma cells/2ml. For group 1, 30 mice were sacrificed at 1, 4, 24, 48 and 72 hours for biodistribution studies. In group 2, 158 mice were divided into 9 groups (n=16 approximately 18/groups)each receiving respectively tumor alone, tumor with normal saline, cold colloid or hot colloid with 16, 23, 31, 46, 62, or 124 MBq activity. Each of these colloid groups was further divided into two groups, one receiving smaller particle sizes (<3 microm:80.4 +/-7.2%, colloid 1) and the other receiving larger particle sizes (<3 microm:12.3+/-1.0%, colloid 2). The animals were checked daily until death and their survival recorded.

RESULTS

Colloid 2 showed higher accumulation in almost all tissues, the highest accumulation organ was tumor ( approximately 40%), then spleen ( approximately 20%), stomach ( approximately 15%), diaphragm ( approximately 3%), and liver ( approximately 2%). There was a significant increase in survival time with increasing amount of the larger-particle-size colloid. Administered levels of 16-31 MBq/mouse were most efficacious and with higher amounts the survival times decreased significantly below that of the controls. There was a significant difference in the dose-response curves for the two preparations. Protection factors (1/Relative-risk) of nearly 5 were achieved using the larger colloid size, and nearly 30 using the smaller colloid size. An amount of 16-31 MBq of the colloid 2 was the optimal activity in these studies. On the one hand, the survival data agreed well with the biodistribution data, where higher accumulation was found in tumor with colloid 2.

CONCLUSION

Rhenium-188 offers on-site availability, medium half-life, higher beta-particle energy of 2.12 MeV for therapy and emission of 155keV gamma photon suitable for imaging. The present study demonstrated that 188Re-sulfur colloid is an effective agent in controlling tumor cells in the abdominal cavity in animals.

Butachlor, a suspected carcinogen, alters growth and transformation characteristics of mouse liver cells

Butachlor is a widely used herbicide in Asia and South America. Previous investigations have indicated that it is a suspected carcinogen. To understand more about the biological effects of butachlor on cultured cells and the mechanism(s) of its carcinogenicity, we studied the alteration of the growth characteristics that was induced by butachlor in normal mouse liver cells (BNL CL2). This study demonstrates that butachlor decreases the population-doubling time of BNL CL2 cells, suggesting that it stimulates cell proliferation. To support this finding, a thymidine incorporation assay was conducted and a similar result that butachlor stimulates cell proliferation was elucidated. In addition, we show that butachlor increases the saturation density of the BNL CL2 cells. When combined with the tumor initiator N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), butachlor transforms cells efficiently, as demonstrated by loss of contact inhibition. These findings indicate that butachlor alters the growth characteristics of BNL CL2 cells and suggest that butachlor may induce malignant transformation through stimulation of cell proliferation, alteration of cell cycle regulation, and suppression of cell density-dependent inhibition of proliferation.

Sputum induction to improve the diagnostic yield in patients with suspected pulmonary tuberculosis

OBJECTIVE

To evaluate the utility of sputum induction in the large-scale tuberculosis control program.

METHODS

Prospective study on sputum induction for improving the diagnostic yield of pulmonary tuberculosis, and estimation of the direct costs for sputum induction.

RESULTS

Of 1,648 tuberculosis suspects with poor or absent sputum production, induced sputum was smear-positive in 558 patients (353 previously smear-negative, 97 inadequate sputum and 108 unproductive). The direct cost per induced sputum was US $0.37.

CONCLUSION

Sputum induction is an effective, low-cost, and simple technique for improving the smear-positive case detection rate in a tuberculosis control program.

[MRI staging of endometrial carcinoma]

Thirty-one patients clinically suspected for endometrial carcinomas were evaluated by MRI. MR imaging findings were compared with surgico-pathologic staging of the tumor following hysterectomy. The MR appearance of endometrial carcinoma included uterine enlargement, endometrial thickness greater than 1 cm, and nodular-massive pattern which was observed mainly on T2-weighted imaging. The tumor on T2-weighted image was of high homogeneous signal intensity and was indistinguishable from surrounding endometrium. When the junctional zone of endometrium-myometrium, so-called low signal zone, depicts segmental interruption or disappearance, it indicated that the tumor had invaded into the myometrium. If cervical canal was widened, with heterogeneous distribution of high signal intensity, cervical involvement by the tumor was demonstrated. According to criteria of MR staging of endometrial carcinoma proposed by Hricak, the accuracy of our results of MR staging was 87%. Therefore, we suggest that preoperative MR examination is useful for staging of endometrial carcinoma.

[Value of MR imaging in the staging of rectal carcinoma]

Correlative studies of MRI and pathologic specimens were done in 35 patients with rectal cancer. The MR manifestations of the primary tumor and its invasion into the surrounding structures were investigated with reference to the staging of rectal cancer. Prone positioning and the procedure of hypotonic air-distension of rectum was the method of choice to depict the primary tumor and tumor invasion. The spin-echo (SE)pulse sequence with TR/TE: 500/32 ms (T1-weighted image) was selected to show the anatomical structures in the pelvis and tumor spread in the surrounding fatty space and lymph node metastasis. Owing to the reduced contrast between tumor invasion and fatty tissue and decreasing signal intensity on multi-echo T2-weighted images the long repetiting time (TR) pulse sequence could not provide significant contribution in tumor staging. The MR appearance of rectal carcinoma was categorized as polypoidnodular, cauliflowermassive and protuberant-ring types. Ulceration was often seen in the latter two types. Peripheral invasion often manifested as spotty-nodular, sawtoothed-wavy and tumefied shape with medium signal intensity on T1-weighted images. The presence of a lump of small nodes, round or oval nodules within 2 cm from the rectal wall or nodular mass in the perirectal fatty space could be considered as possible lymph node metastasis. Following the modified Dukes Staging System of rectal cancer proposed by Astler-Coller all patients were staged preoperatively and correlated with surgical specimens. The accuracy of staging was 74.3%, compatible with the results of studies published.

Biotransformation of butachlor through mercapturic acid pathway in rat tissue homogenates

The metabolism of butachlor was studied in rat liver and kidney homogenates. In vitro incubation of butachlor with liver fractions (S9, microsome, and cytosolic fractions) formed a considerable amount of butachlor glutathione conjugate (BGSC), while the conjugating activity was not efficient for the kidney S9 fraction. There is a sex difference in the distribution of glutathione S-transferase in the liver. It seems that more enzyme activity is detected in the female liver microsome, while this is not the case in its cytosolic fraction. Further biotransformation of BGSC to mercapturate was not observed in the liver S9 fraction. This metabolite was further transformed to butachlor acetyl cysteine conjugate (BACC) in the presence of acetyl CoA, but to butachlor cysteine conjugate (BCC) in the absence of acetyl CoA. These findings demonstrated that butachlor is initially conjugated with GSH to form BGSC by the enzyme glutathione S-transferase in the liver. This metabolite is apparently transported to the kidneys, where it is transformed to the mercapturate.

Analysis of Epstein-Barr virus DNA in nude mouse-passaged nasopharyngeal carcinoma tissues

DNAs extracted from two series of nude mouse-passaged nasopharyngeal carcinoma (NPC) tissues, NPC-295 and -306, and P3HR1 cells were digested with restriction enzyme Bam HI, then electrophoresed on agarose gel and analysed for the Epstein-Barr virus (EBV) DNA fragments by Southern hybridization with 27 radioactive Bam HI DNA fragments and the Eco RI Dhet DNA fragment from cloned EBV DNA of B95-8 cell line. Constant hybridization patterns were revealed in these experiments and the results suggest a stable existence of EBV DNA including replicative form and episomal form in these tissues even after a long time of passage. Neither deletion in YH region nor in I region could be detected when using Bam HI Y, H and I as probes, suggesting the EBV in these tissues are "more complete" viruses. When Bam HI F was used as a probe, an extra Bam HI site was revealed in the analysis of the DNA from NPC-295 suggesting the polymorphism of DNA present in this region. Restriction maps of EBV DNAs in both nude mouse-passaged NPC tissues are proposed. The results suggest that nude mouse-passaged NPC tissue is a good model to study the structure of EBV DNA in tumor tissue.