In normal individuals, heart rate in sinus rhythm varies widely in the course of a 24-hour period, chiefly under the control of the autonomic nervous system. These fluctuations in heart rate can be quantified and the results are referred to as measures of “heart rate variability” (HRV). Time and frequency domain measures of HRV reflect the balance between cardiac sympathetic and para-sympathetic tone during the recording period. This article begins by reviewing the methods and problems of measuring heart rate variability. Impaired HRV is seen in patients following myocardial infarction and is a marker of adverse prognosis, especially of major arrhythmic complications. Acute myocardial infarction affects measurements of HRV. We discuss what can be deduced from abnormally low measures of HRV after infarction. Whether impaired HRV is causally related to arrhythmias or merely an epiphenomenon is then reviewed. The article shows the possible role of heart rate variability as a means of risk stratifying patients after infarction and how the technique could be combined with other tests to optimize risk prediction.

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Sedation is required for echocardiography in the pediatric age group for accurate diagnosis and reliable studies. The drugs used for sedation for echocardiograms include chloral hydrate and midazolam. Though chloral hydrate continues to be used, there may be concerns regarding its safety. Midazolam may have advantages, especially with the oral form of the drug. The status of these drugs and the role of sedation for other procedures in pediatric cardiology are included.

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The choice of treatment strategy from medical therapy, percutaneous transluminal coronary angioplasty (PTCA), and coronary artery bypass grafting (CABG) greatly influences outcome of patients with chronic coronary artery disease. Recent randomized trials and registries provide information as to the judgment of optimal treatment strategy. These studies have shown that best outcome is likely when 1- or 2- vessel disease without proximal left anterior descending artery (LAD) stenosis is treated medically. 2-vessel disease with proximal LAD stenosis or 3-vessel disease without proximal LAD stenosis is treated by PTCA or CABG. 3-vessel disease with proximal LAD stenosis or left main coronary stenosis is treated by CABG. CABG is preferred to PTCA in diabetic patients and patients with decreased left ventricular function. Recent advances in the treatment of coronary artery disease are also reviewed as they influence current treatment strategy.

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Hypertensive disorders occur in about 3-10% of all pregnancies (1,2), and account for significant fetal and maternal morbidity and mortality. They fall into four major categories: chronic hypertension, Preeclampsia-eclampsia (pregnancy induced hypertension), chronic hypertension with superimposed preeclampsia and gestational hypertension. The pathophysiology and treatment of hypertensive disorders in pregnancy is discussed.

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A new product called as BioZ System using electrical bioimpedance is described to provide useful clinical hemodynamic data. Its easy application expands its uses from the intensive care setting to the outpatient clinic. Its reliability has been tested against the traditional Swan Ganz technique. Bioimpedance is useful in various clinical settings such as in the management of congestive heart failure, early diagnosis of transplant rejection, monitoring drug cardiotoxicity, and differentiation of cardiac versus pulmonary causes of dyspnea.

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