Diagnostic significance of serum CK-MB elevations following surgical damage to skeletal muscles

Risk and determinants of myocardial injury during off-pump coronary artery bypass grafting

Perioperative myocardial injury (PMI) after coronary revascularization (bypass surgery using cardiopulmonary bypass or percutaneous intervention) is strongly associated with future adverse events, such as death, myocardial infarction, and coronary intervention. The incidence, determinants, and prognostic significance of PMI after bypass surgery without cardiopulmonary bypass (off-pump surgery) are unknown. The study population comprised the patients who were randomized to off-pump surgery in the Octopus Study. PMI was defined by a creatine kinase isoenzyme-MB/total creatine kinase ratio of >5% during the first 48 hours, postoperatively. PMI occurred in 137 of 260 patients (52%). Using multivariate regression analysis, age, female gender, previous myocardial infarction, preoperative nitrate use, preoperative diuretic use, and number of grafts were independently associated with an increased risk of PMI during off-pump surgery. The presence of preoperative coronary collaterals showed a negative association with PMI. The occurrence of PMI had a crude odds ratio of 7.53 (95% confidence interval 1.59 to 35.63) for an adverse cardiac event at 1 year after off-pump surgery. This odds ratio changed little after adjustment for confounders (odds ratio 6.39, 95% confidence interval 1.41 to 28.93). In conclusion, more severe atherosclerotic disease and female gender were associated with an increased risk of perioperative myocardial injury during off-pump bypass surgery, although the presence of coronary collaterals appeared to be protective. Patients with perioperative myocardial injury during off-pump surgery were at a higher risk of adverse cardiac outcomes at 1 year.

Role of Coronary Collaterals in Off-Pump and On-Pump Coronary Bypass Surgery

BACKGROUND

Collaterals limit infarct size, preserve viability, and reduce mortality in patients with acute myocardial infarction. In patients with stable coronary disease, collaterals are associated with less angina and ischemia during angioplasty and fewer ischemic events during follow-up. The role of collaterals has not been studied in patients undergoing off-pump or on-pump bypass surgery.

METHODS AND RESULTS

The population consisted of the 281 patients randomized to off-pump or on-pump CABG in the Octopus Study. Collaterals were defined on the baseline angiogram with the Rentrop score and were present in 49% and 51% of the patients in the off-pump and on-pump group, respectively. Perioperative myocardial infarction was defined by a creatine kinase-MB to CK ratio >10% and occurred in 18.2% in the off-pump group and 32.5% in the on-pump group. The unadjusted OR of perioperative myocardial infarction in the presence of collaterals was 0.31 (95% CI 0.17 to 0.84) in the off-pump group and 1.06 (95% CI 0.29 to 3.85) in the on-pump group After adjustment for age, gender, hypertension, hypercholesterolemia, diabetes, multivessel disease, ventricular dysfunction, incomplete revascularization, and ischemic time, the OR was 0.34 (95% CI 0.14 to 0.84) in the off-pump group and 1.28 (95% CI 0.30 to 5.40) in the on-pump group, respectively. Kaplan-Meier estimates of event-free survival at 1 year were 87% in patients with and 69% in those without collaterals after off-pump CABG. These estimates were 66% and 63%, respectively, after on-pump CABG.

CONCLUSIONS

Collaterals protect against perioperative myocardial infarction during off-pump surgery but not during on-pump surgery and are associated with a better 1-year event-free survival.

Threshold energy dose for enzyme release after direct-current countershock

Serial measurement of serum total creatine kinase and creatine kinase MB isoenzyme was prospectively performed by photometric assay in 82 consecutive patients (55 male and 27 female; mean age 62 +/- 11 years) after elective DC countershock for atrial flutter or fibrillation. Enzyme release is commonly observed to follow DC shock; the related energy threshold for enzyme release, however, a parameter with potential clinical usefulness, has not yet been determined. The energy dose was individually titrated but the anterolateral paddle-electrode location was used in all cases. The mean +/- S.D. (range) of shock number, peak energy level and cumulative energy dose normalized to body weight were respectively: 1.7 +/- 0.9 (1-5), 228.6 +/- 87.6 (75-400) J and 5.26 +/- 3.74 (1.0-19.7) J/kg. All these parameters had highly significant positive correlation with enzyme release (P < 0.0001), which peaked 16 h after countershock. Only creatine kinase levels changed significantly vs. baseline (P < 0.0001). As evidenced by dose vs. effect scattergram, the energy threshold value for enzyme release was around 4 J/kg for creatine kinase and 6 J/kg for creatine kinase MB isoenzyme. These energy dose figures may provide clinical usefulness to avoid unnecessary muscle damage; moreover, they may be used as a reference when enzyme elevations interfere with the diagnosis of a concomitant ischemic acute myocardial infarction.

Creatine kinase and creatine kinase-MB release after nontraumatic cardiac arrest

The aim of the study was to describe the course of serum creatine kinase (CK) and its MB fraction (CK-MB) in patients surviving cardiac arrest, and to identify factors influencing CK and CK-MB release. The study was set in the community of Vienna, Austria. Data concerning cardiopulmonary resuscitation, collected within a period of 33 months, were evaluated retrospectively and compared with laboratory blood investigations collected prospectively (on admission and after 6, 12, and 24 hours) in 107 adult patients surviving a witnessed cardiac arrest for 24 hours. CK and CK-MB were elevated in >75% of the patients within 24 hours. Release of CK and CK-MB was mainly associated with electrocardiographic evidence of acute myocardial infarction (AMI) cumulative energy administered during defibrillation, and duration of chest trauma by compression. The CK-MB/CK ratio was elevated in 32% of the patients. Of patients with electrocardiographic evidence of AMI, only 49% had an elevated CK-MB/CK ratio. In conclusion, the elevation in serum CK and CK-MB fraction in patients after nontraumatic cardiac arrest is a frequent finding, and is associated with ischemic myocardial injury, as well as physical trauma to the chest. This should be considered when interpreting the course of CK and CK-MB fraction for the diagnosis of AMI.

Elevation of serum creatine kinase in divers with arterial gas embolization

BACKGROUND

Arterial gas embolism due to pulmonary barotrauma and the resultant cerebral gas embolism are catastrophic complications of diving. Previous studies have only rarely noted evidence of gas embolism to noncranial sites.

METHODS

Among 142 persons with diving-related injuries evaluated between January 1982 and July 1991, we identified 29 who had arterial gas embolism and who underwent biochemical studies indicative of muscle injury. Of the 29 patients, 4 were excluded because cardiopulmonary resuscitation had been performed and 3 were excluded because the duration of their dives met or exceeded standard limits set for dives not requiring staged decompression. The outcome at the time of hospital discharge in the remaining 22 patients was correlated with clinical factors and the results of biochemical studies. We also studied 22 subjects after uncomplicated dives and 11 patients who had sustained blunt trauma.

RESULTS

All the patients with diving-associated gas embolism had elevated serum creatine kinase activity (normal, < or = 175 U per liter); the values were markedly elevated (> 900 U per liter) in 14. The MB isoenzyme of creatine kinase was detected in the serum of 13 of 20 patients in whom it was measured and was > or = 4 percent of total creatine kinase activity in 6 patients. In three patients electrocardiography showed myocardial injury. Changes in serum creatine kinase activity of similar magnitude were not present in the subjects who had uncomplicated dives or in the patients with blunt trauma. Thirteen patients recovered fully, four had minor residual neurologic deficits, three were severely impaired, and two died. Logistic-regression analysis revealed a significant correlation between peak serum creatine kinase values and clinical outcome.

CONCLUSIONS

Biochemical evidence of muscle injury is frequently found after diving-associated arterial gas embolism. The correlation between serum creatine kinase activity and outcome suggests that serum creatine kinase is a marker of the size and severity of arterial gas embolism.

The post-operative electrocardiogram and creatine kinase: implications for diagnosis of myocardial infarction after non-cardiac surgery

The objective of this study was to evaluate different approaches to the diagnosis of post-operative myocardial infarction. A total of 232 patients, mostly hypertensive and/or diabetic patients, who were undergoing elective non-cardiac surgery were evaluated pre-operatively. They were followed serially from the day of operation to discharge or the sixth post-operative day with daily clinical evaluations, electrocardiograms, creatine kinase and creatine kinase isoenzymes. In total 22% (51/232) of the patients had post-operative ECG changes in two or more leads. Only 1% developed new Q waves; most of the changes involved changes in the T or ST segments. Seventy percent of patients who had changes in their electrocardiogram were completely asymptomatic. The highest risk of ECG changes or symptoms occurred on the day of operation and the first post-operative day; evidence of post-operative infarction was infrequent after the second post-operative day. Creatine kinase levels rose an average of 250-300 IU on the first and second post-operative day (also the peak time for post-operative ECG changes), reducing its utility as an adjunct to the diagnosis of post-operative infarctions. Importantly, 52% (12/23) of the patients who had greater than or equal to 5% MB isoenzyme had neither ECG changes nor symptoms; the diagnosis of a myocardial infarction should not be made in these patients. In summary, most patients who experience ischemia or infarction post-operatively are asymptomatic. Symptoms should not be required for the diagnosis of post-operative infarction. Seemingly minor differences in criteria can produce major discrepancies in post-operative myocardial infarction rates (from 1 to 9%). The development of a final set of criteria will require further study but the diagnosis of post-operative infarction should probably be based on ECG changes, their duration and consistency, and the association of a positive MB fraction.

[Blunt heart injuries]

Cardiac injuries were present in 16% of our patients suffering from blunt chest trauma. 25% of these cases had no concomitant rib fractures. Sonography is extremely important for evaluation. In myocardial contusion the electrocardiogram reveals mainly disturbances in repolarisation (66 out of 108 patients) and rhythm disturbances (59 patients). A ratio of CK-MB isoenzyme/total CK of over 8% is highly suggestive of myocardial injury. Continuous monitoring in ICU is mandatory. Prognosis is mainly based on additional injuries. Heart wall rupture and luxation of the heart require operative treatment. Lesions of the aortic valves are the most frequent valve injuries.

[Creatine phosphokinases and serum and urinary myoglobin following a procedure in prolonged knee-chest position for the treatment of spondylolisthesis]

Rhabdomyolysis following the knee-chest position was studied in 15 patients scheduled for surgery for spondylolisthesis. A comparison was made between 11 patients scheduled for orthopaedic surgery: ligamentoplasty (6 patients), total hip prosthesis (5 patients) and 11 patients scheduled for long oral surgery. The measurements carried out were blood CPK before surgery, 4, 8, 12 and 24 h after the beginning of surgery, and at days 2, 3 and 4. Blood and urinary myoglobin were measured at days 1, 2, 3 and 4 after surgery. The results were tested with the Mann and Whitney test. There was no statistical change in CPK and myoglobin in the test population. Following the knee-chest position, there was a statistical increase of CPK in all patients, with great individual variations. Myoglobinaemia and myoglobinuria were observed in six patients, these not being correlated with the variations of CPK. Nevertheless, the maximal increase of CPK and myoglobin was seen in one patient, without any modification of diuresis but with an increase of creatininaemia at 220 mmol X l-1. In this series, rhabdomyolysis was real. CPK was not a good index of the release of haematic pigments, the only dangerous ones. A qualitative search for myoglobinuria is suggested, this being followed, or not, by alkalization to prevent acute renal failure.

Creatine kinase (CK): its use in the evaluation of perioperative myocardial infarction

Establishing the diagnosis of acute perioperative myocardial infarction by the mere presence of a serum CK-MB band alone is not valid. Laboratory investigations have shown that tissues other than ventricular myocardium hold appreciable quantities of CK-MB. Moreover, each of the laboratory methods commonly used for measuring serum total CK and its isoenzymes have inherent strengths and weaknesses. Hence, accurate evaluation of perioperative CK-MB bands requires determination of the amplitude and the temporal course of the elevation. Confirmation of the CK-MB findings by analysis of another enzyme system is advisable. Serum lactate dehydrogenase isoenzymes can fulfill this role. Institution of a dual enzyme evaluation is achieved easily in most hospitals and can yield a very high degree of sensitivity and specificity. The final step in diagnostic accuracy is completed by continuing evaluation of the enzyme diagnostic system in each individual institution.

The enzymology of skeletal muscle disorders

In myopathic disorders, abnormal serum enzyme activities are seen primarily in diseases of skeletal muscle where the condition involves the muscle fibers themselves. In denervation myopathies, serum enzyme activities are usually normal. The most dramatic increases of serum enzymes, particularly creatine kinase, are found in the dystrophic diseases, particularly Duchenne dystrophy. A review is given here of the many causes of abnormal serum enzyme activities where the source of enzymes is believed to be skeletal muscle. These include the dystrophies, various types of trauma, exercise, drug- and poison-induced causes including alcohol, malignant hyperthermia, inflammatory diseases, and miscellaneous causes. Tissue and serum activities are summarized for the commonly performed serum enzymes, i.e., CK, LD, AST, and aldolase. An extensive tabular and current description of the various types of dystrophies is given along with serum CK and pyruvate kinase activities.

'Cardiac' enzymes after transurethral resection of the prostate

Postoperative serial determinations of serum total creatine kinase (CK) and the CK-B subunit (by immunoinhibition), and of total lactate dehydrogenase (LD) and isoenzyme LD-1 (by immunoprecipitation), were performed in 16 and 9 patients, respectively, after uncomplicated transurethral resection of the prostate (TURP). Total CK remained unchanged. An early, modest increase in serum CK-B activity, accompanied by an unusually high CK-B/total CK relation, correlated significantly with duration of operation and amount of tissue resected. A slight, early elevation of the total LD level was not accompanied by an increase in LD-1. If the possibility of small increases in CK-B and LD from the prostate is taken into consideration, routine criteria for diagnosing myocardial damage may be applied after TURP.

Myocardial injury and CK-MB release during aortic valve surgery with selective coronary perfusion

The postoperative serum activity of creatine kinase MB isoenzyme (CK-MB) was studied in 25 patients undergoing isolated aortic valve replacement (Björk-Shiley prosthesis). Hypothermia at 30 degrees C and selective coronary perfusion (CP) were used for myocardial protection. Repeated electrocardiograms revealed no signs of perioperative myocardial infarction. In all patients, CK-MB was detected in the serum. The CK-MB as a percentage of total CK at peak CK-MB [12 +/- 1 (mean +/- SEM)] was of the same magnitude as that found in acute myocardial infarction (AMI). Peak CK-MB occurred 2 +/- 0 h after the end of surgery. Peak total CK occurred after 17 +/- 3 h, and the plasma half-life for total CK was three times that of CK-MB. Thus, the kinetics of serum CK differed from those in AMI, but were similar to those reported after coronary bypass operations. The release of CK-MB, as well as of asparatate aminotransferase and thermostable lactate dehydrogenase, was related to the duration of aortic cross-clamping (AC), with a marked increase after 90 min. In two subgroups with similar AC time, postoperative CK-MB activity was higher in the subgroup with longer CP, indicating that CP as a method of myocardial protection may be entirely beneficial.