Predictive implications of ventricular premature contractions associated with treadmill stress testing

Follow-up data on future coronary events was collected on 6,500 patients who had undergone stress testing; 1,327 of these exhibited ventricular premature contractions (VPCs) associated with one or more phases of treadmill stress testing (TSTs). Eighty-three percent of all patients tested had known or suspected cardiovascular disease. The annual incidence of new coronary events (myocardial infarction, angina, cardiac death) during a five year follow-up was 1.7% among 1,067 patients without VPCs or ischemic ST changes, 6.4% in 758 patients with VPCs alone, 9.5% among 609 patients with ischemic ST changes alone and 11.4% in 569 patients with VPCs plus ischemic ST changes. The significance of VPCs associated with the TSTs rests largely upon the clinical status of the persons tested. VPCs observed among patients referred for TSTs for the evaluation of known or suspected cardiovascular disease, with or without ischemic ST abnormalities, represent a definite risk factor for future coronary events.

Intrasubject variation of warfarin binding to protein in serum of patients with cardiovascular disease

A study of 31 patients with cardiovascular disease who were taking warfarin regularly had shown pronounced intersubject differences in serum protein binding of warfarin and a highly significant correlation between the body clearance of warfarin and the free fraction of the drug in serum. Similar observations have been made in experimental animals and are consistent with predictions based on theoretical considerations. The purpose of this investigation was to determine the intrasubject variation in the free fraction of warfarin in serum. Samples of serum were obtained from 23 of the 31 patients previously studied. The time interval between the two studies was 3.4 to 5.7 mo. The daily dose of warfarin had been changed by 10.6% on the average. With two exceptions, there was no change in concurrent medications. The ratio of free fraction values of warfarin in serum, second/first study, was 0.948 +/- 0.297 (mean +/- S.D.), and there was a highly significant correlation (P less than 0.001) between the individual free fraction values in the first and second studies.

Patient selection for anticoagulant therapy in coronary heart disease

Short-term anticoagulant therapy given after an acute myocardial infarction is directed toward preventing thromboembolism and is fairly safe. Long-term anticoagulant therapy prevents coronary thrombosis in selected patients with coronary heart disease (CHD), but carries an appreciable risk of hemorrhage. A decision for or against short-term therapy should be based on an assessment of the immediate risk of thromboembolism. Similarly, the risk of coronary thrombosis should be the major determinant in a decision for or against long-term anticoagulation. The most important information emerging from the clinical trials of long-term anticoagulant therapy in CHD concerns the significant benefit observed among patients with advanced disease.

Cardiac pacing for cardiac arrest due to hyperkalemia plus digitalis and quinidine toxicity

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Serum protein binding as a determinant of warfarin body clearance and anticoagulant effect

The serum protein binding and elimination kinetics of warfarin were determined in 31 patients with cardiovascular disease who were taking warfarin regularly. The free fraction of warfarin in the serum ranged from 0.00436 to 0.0189, indicating 98.11% to 99.56% protein binding. There was no apparent relationship between the extent of protein binding of warfarin and the concentration of albumin or total protein in the serum. The estimated total body clearance of warfarin in the patients ranged from 1.16 to 4.35ml/hr/kg of body weight and correlated significantly with the free fraction of warfarin in serum. This correlation has been predicted on theoretical grounds and shows that serum protein binding is a major determinant of the elimination kinetics of warfarin in man and an important cause of interindividual variations in its body clearance. The interindividual variation of free warfarin concentrations in the serum of patients with similar prothrombin times was somewhat smaller than the variations in total serum-warfarin concentrations and in the daily dose of warfarin. There was no correlation between prothrombin time and the concentration of free warfarin in serum, indicating that variables other than protein binding also affect the anticoagulant response of patients.

Clinical implications of warfarin interactions with five sedatives

The intensity, uniformity and time course of anticoagulant interference by phenobarbital, secobarbital, glutethimide, chloral hydrate and methaqualone were systematically investigated in 16 patients receiving coumarin therapy. Each subject received an individualized fixed daily dose of warfarin and served as his own pre- and postsedative treatment control. Prothrombin times were measured four times weekly during five long-term experiments. Anticoagulant inhibition was observed during the administration of phenobarbital, secobarbital and glutethimide; there was no significant change in prothrombin test results during the trials of chloral hydrate and methaqualone. Barbiturates and glutethimide should not be administered to patients receiving coumarin drugs. The concurrent use of drugs from these groups is decreasing according to a survey of 200 hospital medical records. Chloral hydrate and methaqualone interact pharmacologically with orally administered anticoagulant agents, but the effect is not clinically significant. It is concluded that chloral hydrate and methaqualone may be administered safely without additional caution in prothrombin test monitoring during oral anticoagulant therapy.

Don't use the wrong vitamin K

The emergency use of vitamin K is essentially limited to the reversal of drug-induced hypoprothrombinemia. In patients with adequate liver function, phytonadione acts promptly and predictably in this capacity whereas the derivatives of menadione counteract coumarin drugs only slightly or not at all. It is dangerous to rely on menadione analogues, and these drugs should be removed from emergency room drug stores.