Catecholamines, cigarette smoking, arrhythmias, and acute myocardial infarction

Coronary Atherosclerosis: Pathophysiologic Basis for Diagnosis and Management

Coronary atherosclerosis is a long lasting and continuously evolving disease with multiple clinical manifestations ranging from asymptomatic to stable angina, acute coronary syndrome (ACS), heart failure (HF) and sudden cardiac death (SCD). Genetic and environmental factors contribute to the development and progression of coronary atherosclerosis. In this review, current knowledge related to the diagnosis and management of coronary atherosclerosis based on pathophysiologic mechanisms will be discussed. In addition to providing state-of-the-art concepts related to coronary atherosclerosis, special consideration will be given on how to apply data from epidemiologic studies and randomized clinical trials to the individual patient. The greatest challenge for the clinician in the twenty-first century is not in absorbing the fast accumulating new knowledge, but rather in applying this knowledge to the individual patient.

The smoking-thrombolysis paradox and acute ischemic stroke

Smokers with acute myocardial infarction have better outcomes after thrombolysis than nonsmokers. The authors evaluated the independent effect of smoking on short-term outcome following IV thrombolysis for acute ischemic stroke. After adjusting for covariates, recent smokers who received thrombolysis had a significantly greater drop in 24-hour median stroke severity scores from baseline than nonsmokers who received thrombolysis and lower mortality over 1 year.

Negative inotropic effect of lidocaine in patients with coronary arterial disease and normal subjects

The effect of administration of lidocaine on left ventricular performance was studied using systolic time intervals in nine normal subjects, eight patients with stable angina, and 15 patients with acute myocardial infarction. The greatest response in systolic time intervals occurred at three minutes after intravenous injection of lidocaine (100 mg), with values returning to baseline at 10 to 15 minutes. Administration of lidocaine produced a significant prolongation of the preejection period (PEP) corrected for heart rate in all groups and a prolongation of the ratio of PEP to left ventricular ejection time (PEP/LVET) in patients with angina. The group with acute myocardial infarction exhibited a hyperadrenergic state, as shown by a short baseline QS2I. The QS I was lengthened by administration of lidocaine in all groups, but this was more profound in those with acute myocardial infarction. These changes in systolic time intervals were still present at two hours after injection in six patients with acute myocardial infarction in whom an infusion of lidocaine followed the initial bolus. The effect of administering lidocaine after intravenous injection of propranolol (5 mg) was also studied in six normal subjects. Although propranolol therapy along prolonged the PEP/LVET, a further significant prolongation followed subsequent injection of lidocaine.

Left ventricular function and adrenergic hyperactivity before and after saphenous vein bypass

Forty patients with severe angina pectoris were studied before and two weeks after saphenous vein bypass surgery (SVG) in order to assess the effect of this operation on left ventricular performance as judged by systolic time intervals (STI). The patients were divided into two groups: group I included 29 patients in whom no postoperative infarction occurred and group II was composed of 11 patients with postoperative infarction. For group I the PEP/LVET was 0.39 +/- 0.01 preop and slightly but significantly increased at 0.42 +/- 0.004 (P less than 0.025) two weeks postop. The mean preop PEP/LVET was 0.33 +/- 0.01 for group II and dramatically increased to 0.54 +/- 0.02 (P less than 0.001) after surgery. Another striking abnormally was a marked shortening of electromechanical systole (QS2I), which was uniformly present in the postoperative studies. Follow-up studies in 16 patients and urinary catecholamine determination in five patients suggested excessive adrenergic activity was responsible for the abbreviated QS2I. This phenomenon must be considered when interpreting the results of SVG on left ventricular function.

Usefulness of systolic time intervals in coronary artery disease

This review summarizes current knowledge concerning the value of systolic time intervals in coronary artery disease. Although the usual pattern of prolongation of the preejection period (PEP) and shortening of the left ventricular ejection time (LVET) characteristic of left ventricular failure is seen in acute myocardial infarction, the systolic time intervals (as well as all other measures) are profoundly influenced by adrenergic hyperactivity characteristics of this disorder. Adrenergic stimulation normally shortens both the PEP and LVET indexes and decreases the PEP/LVET ratio. The degree of shortening of electromechanical systole (QS2) is directed related to the excessive adrenergic tone. Patients with the greatest systolic time interval abnormalities have a poorer prognosis, a greater incidence of congestive heart failure and more abnormalities of directly measured indexes of left ventricular performance. The systolic time intervals are useful for assessing left ventricular performance in chronic coronary artery disease as well. In chronic coronary artery disease the PEP/LVET ratio and angiographically determined left ventricular ejection fraction are closely correlated ( r = -0.76), but the level of this correlation is less than that in other forms of left ventricular disease. The left ventricular ejection time index is prolonged after exercise in patients with angina pectoris when compared with findings in normal subjects. Failure of the ischemic ventricle to respond to adrenergic stimulation is the most likely mechanism. Addition of the postexercise left ventricular ejection time to standard treadmill stress testing identifies a significant number of patients (23 percent) who would have had false negative results by electrocardiographic criteria alone. In addition, this index provides confirmatory evidence in those with apparently positive electrocardiographic test data. The systolic time intervals have been useful in assessing both medical and surgical therapy in coronary artery disease. The test can be performed repeatedly and provides a measure of both left ventricular performance and extent of adrenergic hyperactivity. Thus, evaluation of therapy represents the most useful future application of systolic time intervals.