Bradycardia pacing

Rosenthal ME, and Paskman C. Noise detection during bradycardia pacing with a hybrid nonthoracotomy implantable cardioverter defibrillator system incidence and clinical significance. Pacing Clin Electrophysiol 1998 21 1380-1386. 

The ICD circuitry determines how and when both bradycardia pacing and anti-tachycardia therapies are delivered. The sophisticated circuitry... 

Separate pacemaker and ICD devices in the same patient are becoming increasingly rare. This is likely so because contemporary ICDs have generous bradycardia pacing functions, and improved battery longevity. 

A 41-year-old male with severe non-ischemic dilated cardiomyopathy (EF 10%), severe first degree (400 ms PR interval) and LBBB, and medically refractory CHF receives a biventricular ICD and subsequently develops paroxysmal AF (PAF). He initially does well however, his blood pressure limits the ability to treat the PAF, and he presents to your office in florid CHF. The following strip is obtained. The bradycardia pacing mode is DDD with lower rate of 40 p.p.m., upper rate of 150 p.p.m., and mode switching is programmed on. 

ICDs can deliver a range of therapies depending on the arrhythmia detected and how the device is programmed. Some ICDs can also detect and treat atrial arrhythmias or provide biventricular pacing. Therapies include antitachycardia pacing, cardioversion, defibrillation, and bradycardia pacing. ... 

Bradycardia pacing Electrical pacing pulses are used when the heart s natural electrical signals are too slow. ICD systems can pace one chamber (Wl pacing) of the heart at a preset rate or sense and pace both chambers (DDD pacing). 

Acute treatment of patients with second- or third-degree AV nodal blockade consists primarily of administration of atropine, which maybe administered in the same doses as recommended for management of sinus bradycardia. In patients with hemodynamically unstable or severely symptomatic AV nodal blockade that is unresponsive to atropine and in whom temporary or transvenous pacing is not available or is ineffective, epinephrine (2 to 10 mcg/minute, titrate to response) and/or dopamine (2 to 10 mcg/kg/minute) maybe administered.14... 

In sinus bradycardia or incomplete heart block, lidocaine administration for the elimination of ventricular ectopy without prior acceleration in heart rate (eg, by atropine, isoproterenol or electric pacing) may promote more frequent and serious ventricular arrhythmias or complete heart block. Use with caution in patients with hypovolemia and shock, and all forms of heart block. 

Isoprenaline occasionally has a place in the management of cardiac conditions in which bradycardia is a feature, e.g. low cardiac output associated with slow heart rate after extracorporeal circulation in patients with excessive p-blocking therapy. It may also be used in the treatment of overdose with (3-adrenoceptor antagonists and for refractory bradyarrhythmias prior to cardiac pacing. Isoprenaline is used in the treatment of bronchial asthma on account of its 32 effects. 

A 23-year-old woman took chlorpropamide 5-10 g. She needed assisted respiration and cardiac pacing for bradycardia (probably due to blockade of potassium channels), fluid infusion, and forced diuresis for 3 days. Notwithstanding continuous glucose infusion and glucose boluses she relapsed into severe hypoglycemia with convulsions. Only on day 27 was her urine free of chlorpropamide and her blood glucose normal. 

Adverse effects The adverse events associated with (3 blockers may be avoided by starting treatment at very low doses. However, treatment can be associated with complaints of fatigue and weakness, which usually resolve in a few weeks, Sometimes it is necessary to decrease the dose of the (3 blocker or diuretic. Symptomatic bradycardia is another serious adverse effect of (3 blockers, and requires a decrease in the dose or sometimes cardiac pacing to allow the use of this vital medication, Hypotension is another potential side effect however, it is rarely seen as the therapy is started with a very low dose (3,25 mg twice a day for carvedilol, I mg for bisoprolol and 12,5 mg for extended release metoprolol). The administration of ACE inhibitor and diuretic at a different time of day than the (3 blocker can... 

Kahkonen S, Kaartinen M, Juhela P. Permanent pacing-aid to carry out long-term lithium therapy in manic patient with symptomatic bradycardia. Pharmacopsychiatry 2000 33(4) 157. 

Atropine (1-2 mg i.v. as 1 or 2 bolus doses) to eliminate the unopposed vagal activity that contributes to bradycardia. Most patients will also require direct cardiac pacing. 

Clonidine causes sinus bradycardia and atrioventricular block, as illustrated by two cases, one a 10-year-old boy (6) and the other a 71-year-old woman (7), who developed Wenckebach s phenomenon. Clonidine was also studied in seven patients subjected to electrophysiological studies after 5 weeks of therapy (8). It slowed the sinus rate and increased the atrial pacing rate, producing Wenckebach s phenomenon, indicating depressed function of the sinus and AV nodes. 

A 38-year-old white man with a history of coronary artery disease, myocardial infarction, coronary artery by-pass, alcoholism, and depression took a combined massive overdose of diltiazem and atenolol (24). He underwent cardiopulmonary resuscitation because of cardiac arrest bradycardia, hypotension, and oliguria followed and were resistant to intravenous pacing and multiple pharmacological interventions, including intravenous fluids, calcium, dopamine, dobutamine, adrenaline, prenalterol, and glucagon. Adequate mean arterial pressure and urine output were restored only after the addition of phenylephrine and transvenous pacing. He survived despite myocardial infarction and pneumonia. 

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