Arrhythmias bradyarrhythmias

Lethal Arrhythmias. Arrhythmias are a second significant source of cardiovascular problems. An arrhythmia is an abnormal or irregular heart rhythm. Bradyarrhythmias result in heart rates that are too slow tachyarrhythmias cause abnormally fast rates. A bradyarrhythmia can be debiUtating, causing a person to be short of breath, unable to climb stairs, black out, or even to go into cardiac arrest. Tachyarrhythmias can be un settling and painful at best, life-threatening at worst. 

Dmgs that mimic or inhibit the actions of neurotransmitters released from parasympathetic or sympathetic nerves innervating the heart may also be used to treat supraventricular bradyarrhythmias, heart block, and supraventricular tachyarrhythmias. Those used in the treatment of arrhythmias may be found in Table 1. 

Normal rhythmic activity is the result of the activity of the sinus node generating action potentials that are conducted via the atria to the atrioventricular node, which delays further conduction to the His-Tawara-Purkinje system. From the Purkinje fibres, action potentials propagate to the ventricular myocardium. Arrhythmia means a disturbance of the normal rhythm either resulting in a faster rhythm (tachycardia, still rhythmic) or faster arrhythmia (tachyarrhythmia) or slowed rhythm (bradycardia, bradyarrhythmia). 

Diltiazem appears to be similar in efficacy to verapamil in the management of supraventricular arrhythmias, including rate control in atrial fibrillation. An intravenous form of diltiazem is available for the latter indication and causes hypotension or bradyarrhythmias relatively... 

These agents appear to be similar in efficacy to verapamil in the management of supraventricular arrhythmias, including rate control in atrial fibrillation. An intravenous form of diltiazem is available for the latter indication and causes hypotension or bradyarrhythmias relatively infrequently. Bepridil also has action potential- and QT-prolonging actions that theoretically may make it more useful in some ventricular arrhythmias but also create the risk of torsade de pointes. Bepridil is only rarely used, primarily to control refractory angina. 

Sinus tachycardia (due to vagal blockade) is a common feature but abnormalities of cardiac conduction accompany moderate to severe intoxication and may proceed to dangerous tachy- or bradyarrhythmias. Hypoterrsion may result from a combination of cardiac arrhythmia, reduced myocardial contractility and dilatation of venous capacitance vessels. 

This information will be useful in understanding when and why bradyarrhythmias and/or intraventricular conduction abnormalities may occur during an evolving ACS (see Arrhythmias and intraventricular conduction blocks in ACS p. 250). 

Isoproterenol (P, = P2) Rx uses include bronchospasm, heart block, and bradyarrhythmias. May cause flushing, angina, and arrhythmias. 

Heart disease is the leading cause of death in the United States and is responsible for approximately 870,000 deaths per year (1). Sudden cardiac death (SCD) is responsible for almost half of these deaths, claiming 350,000 to 400,000 lives per year (2). SCD is defined by the World Health Organization as death due to any cardiac disease that occurs out of hospital, in an emergency room, or a patient who is dead on arrival to a care facility. Of note, the death must occur within one hour after the onset of symptoms. The majority of SCD is likely arrhythmic in etiology. In women, up to 88% of sudden cardiac arrests may be due to arrhythmic causes (3). Of SCD due to cardiac arrhythmias, greater than 80% of events are due to ventricular tachycardia (VT) and ventricular fibrillation (VF), with the remainder due to bradyarrhythmias and asystole (4). Coronary artery disease (CAD), manifesting acutely as ischemic ventricular arrhythmias or chronically as scar-mediated... 

When the normal sequence of impulse initiation and propagation is perturbed, an arrhythmia occurs. Failure of impulse initiation may result in slow heart rates (bradyarrhythmias), whereas... 

The introduction and manipulation of pacing leads are frequently associated with both tachyarrhythmias and bradyarrhythmias as a lead negotiates the chambers of the right heart. Ventricular tachycardia is extremely common as the pacing electrode or guidewire contacts the right ventricular myocardium. Simple withdrawal of these objects usually terminates the arrhythmia. In extreme cases, sustained monomorphic ventricular tachycardia and even ventricular fibrillation may occur. Some institutions have instituted a policy of placing external defibrillation pads prophylactically in anticipation of required cardioversion. 

Is caused by an increase in calcium above the normal values. Normal calcium levels range from 8.5 to 10.5 mg/dl. Patients may experience bradyarrhythmias, ventricular arrhythmias and heart block (AV nodal block) when the levels of calcium are depleted below normal levels. ECG findings can be non-specific and difficult to distinguish. 

---