digitoxin and Magnesium-Deficiency

Depletion of K and Mg appears to play a significant role in the ventricular tachyarrhythmias seen in alcoholic patients, patients treated with diuretics and/or patients with digitalis toxicity. A therapeutic strategy is suggested by the observation that hypokalemic patients have a 38-42% incidence of concurrent hypomagnesemia: that Mg as well as K should be replenished in all hypokalemic patients who suffer from alcoholism or who are receiving diuretics and/or digitalis because of the ventricular tachyarrhythmias which accompany these clinical states. Routine serum Mg determination will contribute significantly towards identifying patients at risk for cardiac arrhythmias due to Mg depletion.

Topics: Alcoholism; Animals; Arrhythmias, Cardiac; Digitalis; Diuretics; Electrocardiography; Humans; Magnesium; Magnesium Deficiency; Plants, Medicinal; Plants, Toxic; Potassium Deficiency; Rats

Congestive heart failure (CHF) represents a pathophysiologic state in which cardiac output is inadequate to meet the metabolic needs of multiple organ systems. The primary pathologic event in CHF is a marked, sustained reduction in the intrinsic contractility of the heart. A review of the current knowledge regarding the etiology and progression of CHF reveals that it is associated with profound biochemical, peripheral hemodynamic (increased peripheral vascular resistance), and electrolyte disturbances. In addition to sodium and water retention, CHF is often associated with hypokalemia and hypomagnesemia as well as tissue deficits in K and Mg. Cardiac glycosides and diuretics (loop and distal types) often exacerbate, or result in, hypokalemia and hypomagnesemia, which may lead to cardiac arrhythmias and sudden cardiac death. Deficits in extracellular and vascular tissue Mg lead to peripheral vasoconstriction; this together with K deficits and the release of neurohumoral substances may be responsible in large measure for the increase in peripheral vascular resistance commonly noted in CHF. More attention must be paid to the careful monitoring of electrolyte levels (Na, K, Mg) in tissues (possibly lymphocytes) and plasma of CHF patients. Deficits in either K or Mg must be corrected in CHF. The nonspecific vasodilator properties of Mg2+ together with its ability to unload the heart should be considered as an important adjunct tool in the management of CHF.

Topics: Adenosine Triphosphate; Calcium; Coronary Disease; Digitalis; Heart Failure; Humans; Magnesium; Magnesium Deficiency; Myocardial Contraction; Myocardium; Oxygen Consumption; Plants, Medicinal; Plants, Toxic; Potassium; Sodium; Vasopressins

The antiarrhythmic potency of Mg has been described repeatedly since 1935, both as a factor in human disease and in animal experiments. Nevertheless, this therapeutic efficacy is rarely mentioned in textbooks. Both the pharmacological effect of Mg and the correction of Mg deficiency have been used in treatment of digitalis toxicity, variant angina, Torsades de Pointes, as well as in arrhythmia of unknown origin. Mg-deficiency can be caused by malabsorption or by excessive urinary loss. Both situations can occur on a congenital basis. The most frequent cause is probably alcoholism. Iatrogenic factors include digitalis, diuretics, gentamicin, as well as cisplatinum, which appreciably enhance urinary Mg loss. Correction of Mg-deficiency by parental and/or oral administration should lead to recovery. If the cause of the deficiency can be eliminated, once the deficit is repaired it may be acceptable to discontinue the supplement. However, the cause is often multifactorial, requiring further evaluation and treatment.

Topics: Animals; Arrhythmias, Cardiac; Diet; Digitalis; Electrophysiology; Humans; Magnesium; Magnesium Deficiency; Plants, Medicinal; Plants, Toxic; Potassium

The efficacy of magnesium in the prevention of arrhythmias in pediatric patients after heart surgery remains unknown. Therefore we prospectively examined the effect of magnesium treatment on the incidence of postoperative arrhythmias in pediatric patients undergoing surgical repair of congenital heart defects.. Twenty-eight pediatric patients undergoing heart surgery with cardiopulmonary bypass were prospectively, randomly assigned in a double-blind fashion to receive intravenous magnesium (magnesium group, n = 13; 30 mg/kg) or saline (placebo group, n = 15) immediately after cessation of cardiopulmonary bypass. Magnesium, potassium, and calcium levels were measured at defined intervals during surgery and 24 hours after surgery. Continuous electrocardiographic documentation by Holter monitor was performed for 24 hours after surgery. Magnesium levels were significantly decreased below the normal reference range for patients in the placebo group compared with the magnesium group on arrival in the intensive care unit and for 20 hours after surgery. Magnesium levels remained in the normal range for patients in the magnesium group after magnesium supplementation. In 4 patients in the placebo group (27%), junctional ectopic tachycardia developed within the initial 20 hours in the intensive care unit. No junctional ectopic tachycardia was observed in the magnesium group (P =.026).. Although this study was originally targeted to include 100 patients, the protocol was terminated because of the unacceptable incidence of hemodynamically significant junctional ectopic tachycardia that was present in the placebo group. Thus low magnesium levels in pediatric patients undergoing heart surgery are associated with an increased incidence of junctional ectopic tachycardia in the immediate postoperative period.

Topics: Arrhythmias, Cardiac; Calcium; Cardiac Surgical Procedures; Cardiopulmonary Bypass; Child, Preschool; Digitalis; Double-Blind Method; Electrocardiography, Ambulatory; Female; Heart Defects, Congenital; Humans; Infusions, Intravenous; Magnesium; Magnesium Deficiency; Male; Phytotherapy; Plants, Medicinal; Plants, Toxic; Postoperative Complications; Potassium; Prospective Studies; Tachycardia, Ectopic Junctional; Treatment Outcome

Elimination of calcium (Ca), magnesium (Mg) or both from the medium of callus cultures of Digitalis davisiana Heywood, Digitalis lamarckii Ivanina, Digitalis trojana Ivanina and Digitalis cariensis Boiss. ex Jaub. et Spach increased cardenolides production. Callus was induced from hypocotyl segments from one-month old seedlings were cultured on MS medium containing 0.5 μg ml(-1) thidiazuron (TDZ) and 0.25 μg ml(-1) indole acetic acid (IAA). After 30 days of culture, callus was transferred in hormone-free MS medium (MSO) as well as Ca or Mg or both were completely eliminated from same medium. The amount of five cardenolides from D. davisiana Heywood, D. lamarckii Ivanina, D. trojana Ivanina and D. cariensis Boiss. ex Jaub. et Spach were compared. Higher amounts of five cardenolides and total cardenolides were obtained when callus of four Digitalis species were incubated on MS medium lacking both Ca and Mg. The mean contents of total cardenolides obtained were in the order of D. lamarckii (2017.97 μg g(-1))>D. trojana (1385.75 μg g(-1))>D. cariensis (1038.65 μg g(-1))>D. davisiana (899.86 μg g(-1)) when both Ca and Mg were eliminated from the medium, respectively. This protocol is useful for development of new strategies for the large-scale production of cardenolides.

Topics: Calcium; Cardenolides; Culture Media; Digitalis; Hypocotyl; Magnesium; Magnesium Deficiency; Plant Extracts; Plant Somatic Embryogenesis Techniques; Seedlings; Species Specificity; Turkey

In 9 (of 17 attempted) experiments (8 aborted due to premature tissue death), transmembrane electrical activity was recorded from canine false tendons superfused with Mg-free Tyrode's solution to simulate hypomagnesemia. Oscillatory after-potentials (OAP) developed similar to those seen after exposure to 2 X 10(-7) M ouabain, a short-lasting (0.5-1 time the duration of an action potential) OAP that often reached threshold superimposed on a long-lasting (3-4 times as long as the short) OAP. Both forms of OAP were shown to be Ca2+-dependent, as both were prevented by 10(-7) M nifedipine, but only the short OAP were abolished by nifedipine once they had appeared, while high (5 mM = 10 times normal) Mg2+ both prevented and terminated short and long OAP in digitoxic preparations. Results suggest that cardiac glycosides may deplete Mg from the myocardium. The mechanism of the therapeutic action of Mg2+ in digitalis intoxication is discussed in light of its involvement in Ca2+ sequestration by the sarcoplasmic reticulum.

Topics: Animals; Arrhythmias, Cardiac; Calcium; Cardiac Glycosides; Digitoxin; Dogs; Female; Heart; Magnesium; Magnesium Deficiency; Male; Nifedipine; Purkinje Fibers

Topics: Animals; Cardiac Glycosides; Digitoxin; Dogs; Magnesium Deficiency; Potassium Deficiency