Cardiac troponin I is modified in the myocardium of bypass patients

BACKGROUND

Selective proteolysis of cardiac troponin I (cTnI) is a proposed mechanism of contractile dysfunction in stunned myocardium, and the presence of cTnI degradation products in serum may reflect the functional state of the remaining viable myocardium. However, recent swine and canine studies have not demonstrated stunning-dependent cTnI degradation.

METHODS AND RESULTS

To address the universality of cTnI modification, myocardial biopsy samples were obtained from coronary artery bypass patients (n=37) before and 10 minutes after removal of cross-clamp. Analysis of biopsy samples for cTnI by Western blotting revealed a spectrum of modified cTnI products in myocardium both before and after cross-clamp, including degradation products (7 products resulting from differential N- and C-terminal processing) and covalent complexes (3 products). In particular, a 22-kDa cTnI degradation product with C-terminal proteolysis was identified, which may represent an initial ischemia-dependent cTnI modification, similar to cTnI(1-193) observed in stunned rat myocardium. Although no systematic change in amount of modified cTnI was observed, subgroups of patients displayed an increase (n=10, 85+/-5% of cTnI remaining intact before cross-clamp versus 75+/-5% after) or a decrease (n=12, 67+/-5% before versus 78+/-5% after). Electron microscopy demonstrated normal ultrastructure in biopsy samples, which suggests no necrosis was present. In addition, cTnI modification products were observed in serum through a modified SDS-PAGE methodology.

CONCLUSIONS

cTnI modification, in particular proteolysis, occurs in myocardium of bypass patients and may play a key role in stunning in some bypass patients.

Frequency content and sex difference of the Frank lead signal-averaged ECG in a population with significant coronary artery disease. Comparison with concurrent 12-lead ECG morphology

The 12-lead electrocardiogram (ECG) and a 100-beat signal-averaged Frank lead ECG (SAECG) at a sampling rate of 1,000 Hz and with 16-bit resolution were recorded from 52 women and 256 men with significant coronary artery disease presenting for coronary artery revascularization. The QRS portion of each Frank lead was digitally filtered in four bandwidths: 0-10, 10-60, 60-150, and 150-250 Hz. The root-mean-square (RMS) voltage of each filtered signal was calculated as an absolute value and normalized as a percentage of the sum of the four filters, creating 27 variables. Three groups were formed using the presenting 12-lead ECG: N-ECG, ST-ECG, and MI-ECG. Despite variation in 12-lead morphology, concordance was dominant in the RMS values of the SAECG in sex comparisons within and between groups. There was significant sex difference of the RMS values in 6 of the 15 absolute RMS variables within the three groups. Women had no significant between-group difference, and men had a significant between-group differences in five absolute values and one normalized RMS value. P was considered significant at < .05.

Intermittent percutaneous infusion into the hepatic artery of cytotoxic drugs for hepatic tumours

Between June 1, 1976 and Apr. 30, 1981, 157 patients were treated for inoperable cancer of the liver by intermittent percutaneous infusion of chemotherapeutic agents into the hepatic artery. The majority of these patients had metastatic colorectal cancer. The regimen of chemotherapeutic infusion evolved during the study and is described. The survival of the total group of patients is analysed according to type of cancer, extent of disease, dosage and combination of drugs. This therapeutic modality appears to benefit patients with metastases from colorectal cancer confined to the liver. The complication rate for this procedure is relatively low. The results from this study suggest that intermittent percutaneous infusion of cytotoxic agents into the hepatic artery is worthwhile for selected patients and should be studied further in combination with other forms of therapy.