Results of resting and ambulatory electrocardiograms in patients with hypothyroidism and after return to euthyroid status.

Hypothyroidism is not infrequently associated with an abnormally long QTc interval (> or = 450 msec). Rarely, marked prolongation of the QTc interval and malignant ventricular arrhythmias have been reported. In this study, QTc intervals on resting electrocardiograms (ECGs) were compared in 10 patients before and after treatment of hypothyroidism. The QTc interval increased in seven patients during euthyroidism compared with hypothyroidism, and decreased in three patients. During hypothyroidism, the QTc interval was mildly prolonged in 2 of the 14 patients; both had mild decreases in triiodothyronine (T3) or thyroxine (T4). The 24-hour ambulatory ECGs measured during hypothyroidism and after restoration of biochemical euthyroidism also were compared in 9 patients. There was no significant difference in ventricular ectopy. None of the 13 patients assessed during hypothyroidism had > or = 4 beats of ventricular tachycardia. There was no relationship between thyroid-stimulating hormone (TSH) or T3 levels and QTc intervals during hypothyroidism. A moderate correlation between lesser degrees of T4 depression and increasing QTc interval was present. Mild QTc prolongations are relatively common in patients with hypothyroidism and are usually associated with milder degrees of thyroid underactivity, but are not associated with clinically significant ventricular tachyarrhythmias.

Vagally mediated multivessel coronary artery spasm during coronary angiography.

We report on a case of multivessel coronary artery spasm preceded by vagal signs and symptoms, which resolved after administration of atropine. This supports that the spasm was triggered by endogenous acetylcholine.

Resolution of exercise intolerance secondary to ischemic sinus node dysfunction following percutaneous transluminal angioplasty.

We report on a case of significant exertional symptoms secondary to occlusion of a nondominant right coronary artery proximal to the sino-atrial branch, with associated exercise-induced sinus node dysfunction. Successful angioplasty of the occluded right coronary artery restored a normal functional capacity and sinus tachycardia response to exercise.

Indwelling pericardial drainage catheter break secondary to heart movement and catheter angulation.

We report on a case of a pericardial drainage catheter that severed on attempted removal. Surgery was required to remove the retained portion. No manufacturing defects were found on analysis of the catheter. Shear forces due to heart movement and the angle of catheter entry into the pericardium were the suspected reasons for the catheter disruption.

Anomalous origin of left internal mammary artery from the lateral junction of the left subclavian artery and aorta.

We describe the first reported case of an internal mammary artery originating from the junction of the left subclavian artery and aorta. Noting this, along with other reported anomalies and various pathologic conditions, it appears warranted to perform routine preoperative internal mammary artery angiography before coronary artery bypass surgery.

Evaluation of CK and CK-MB in alcohol abuse subjects with recent heavy consumption.

We analyzed CK and CK-MB levels over 24 h in 15 male subjects admitted for alcohol detoxification following recent heavy ingestion. None had clinical or electrocardiographic evidence of myocardial ischemia or infarction. The mean 0-hour serum alcohol level +/- SD was 342 +/- 101 mg/dl. CK levels were measured by Kodak Ektachem and Abbott IMx assays, and CK-MB levels were determined by these assays and the Hybritech isoenzyme test. In 36% of the patients elevated 0-hour CK levels by the IMx and Ektachem assays were observed. The CK levels measured every 8 h decreased so that by 24 h CK was elevated in 1 patient by the Ektachem assay and in 2 by the IMx assay. Only 1 patient (7%) had an elevated 0-hour CK-MB value by two of the three assays, and it is unclear whether the source was cardiac or extracardiac. We conclude that: (1) elevated CK levels are common in heavy alcohol use patients without evidence of myocardial ischemia; (2) CK values over the first 24 h are decremental, not rising and falling as is typical of myocardial infarction and (3) current isoenzyme immunoassays eliminate a cardiac cause for elevated CK in most of these patients. These findings may assist in the evaluation of alcoholic patients with chest pain.

Vasodepressor syncope from neck cancer with associated C-6 dermatome neuralgia.

An unusual case of neck cancer with associated C-6 dermatome neuralgia causing vasodepressor syncope episodes is discussed. Pacemaker therapy proved not to be required. When evaluating syncope with bradycardia, it is important to search for underlying causes and to ascertain whether or not pacemaker therapy is indicated.

Treadmill exercise electrocardiography in the elderly with physical impairments.

Treadmill testing (TMT) was performed on 76 frail but ambulatory subjects, between 64 and 84 years of age, who had common health problems contributing to physical limitations but had no clinically apparent heart disease. The subjects achieved a mean symptom-limited maximal heart rate of 140.1 +/- 2.07 (SEM) beats per minute which was 80.2 +/- 2.1% of the predicted maximum for age. By standard criteria, ischemic responses were noted in only 5 subjects (6.6%). Three responses were categorized as inconclusive (multifocal ventricular ectopy, chest pain without electrocardiographic change, and prompt ST depression upon standing). TMT was well tolerated, with no significant difficulties encountered. Even for those frail elderly with diseases and physical impairments, symptom-limited TMT may be used with low risk to quantify functional capacity and for exercise prescription. Attempts to screen more intensively for cardiac disease may be irrelevant to their immediate need for maintaining function.

Recurrent supraventricular tachycardia induced by antitachycardia pacemaker.

We report a case of sensing malfunction in which supraventricular tachycardia was repeatedly induced, then terminated appropriately, by an antitachycardia pacemaker.

Successful result from delayed streptokinase administration: subtotal thrombotic occlusion in a subsequently normal coronary artery.

This report describes successful results from intracoronary streptokinase administered beginning 6 hr after onset of symptoms to a 32-year-old male with subtotal vessel occlusion by thrombus. Coronary angiography 26 days later demonstrated normal vessels. We conclude that 1) duration of symptoms beyond 3-4 hr should not preclude the use of thrombolytic therapy in evolving myocardial infarction, 2) this patient exemplifies the higher incidence of subsequently demonstrated normal coronary arteries in patients under age 35 with acute myocardial infarction; arterial spasm and platelet aggregation are the most likely causes of coronary occlusion in these patients.

Post-tetanic hyperpolarization, sodium-potassium-activated adenosine triphosphatase and high energy phosphate levels in garfish olfactory nerve.

1. While much is now known about the Na-K-ATPase and the posttetanic hyperpolarization of nervous tissue, they have yet to be studied together in the same preparation. 2. The post-tetanic hyperpolarization was studied in desheathed garfish olfactory nerve. The rate constant of decay of the post-tetanic hyperpolarization was determined by monitoring difference potentials after stimulation at 1/sec for 2-3 min. 3. In membrane fractions prepared from these nerves, the ouabain-sensitive ATPase activity (Na-K-ATPase) was determined by spectrophotometric measurements. 4. Both the post-tetanic hyperpolarization and the Na-K-ATPase showed a similar sigmoidal dependence on K+ concentration. The sequence of cation specificities measured at the K-site of the enzyme was the same as that determined by post-tetanic hyperpolarization measurements in whole nerve. 5. The rate constants of the enzyme showed a dependence on Na+ concentration that paralleled the way in which the post-tetanic hyperpolarization rate constants varied as a function of the number of impulses. When Na+ was completely replaced by Li+, neither enzyme activity nor post-tetanic hyperpolarization could be measured. 6. The pH optimum for enzyme activity was between pH 7-0 and 7-8, while the optimal pH for post-tetanic hyperpolarization was above pH 8-0. 7. Metabolite levels in preparations of this nerve studied in vitro correspond to levels found in vivo. 8. High energy phosphate levels were measured fluorometrically in extracts of nerve samples that had been stimulated in air at 1/sec for various intervals. 9. During the first 2 min of stimulation, there was a significant accumulation of inorganic phosphate, and the ATP/ADP.Pi ratio dropped appreciably. 10. The accumulation of ATPase products was commensurate with the approach of post-tetanic hyperpolarization rate constants to their maximum level. This provides direct evidence for an ATPase functioning in active Na+ transport in nerve. 11. The garfish Na-K-ATPase is sensitive to the ATP/ADP ratio of the incubating medium, but is relatively insensitive to orthophosphate, Pi. The fall in post-tetanic hyperpolarization rate constants observed with continued nerve stimulation may have been partially due to the falling ATP/ADP ratio measured in nerve under similar conditions.