Normal sinus heart rhythm

Monitor the patient for termination of AV nodal blockade and restoration of normal sinus rhythm, heart rate, and alleviation of symptoms. 

Electrocardiograph normal sinus rhythm Chest x-ray slightly enlarged heart Ventilation/perfusion (V/Q) scan high probability of PE... 

A 59-year-old male with a history of rheumatic heart disease is found to have atrial fibrillation (AF for which he is treated with digoxin. Treatment with digoxin converts his AF to a normal sinus rhythm and most likely results in a decrease in which of the following ... 

Ivabradine is used in the treatment of angina in patients in normal sinus rhythm. It acts on the sinus node resulting in a reduction of the heart rate. It is contraindicated in severe bradycardia (heart rate lower than 60 beats/ minute), cardiogenic shock, acute myocardial infarction, moderate-to-severe heart failure, immediately after a cerebrovascular accident, second and third-degree heart block and patients with unstable angina or a pacemaker. Side-effects include bradycardia, first-degree heart block, ventricular extrasystoles, headache, dizziness and visual disturbances, including blurred vision. 

Drugs of this group are calcium channel blockers that inhibit slow transmembrane calcium ion flow in the cell of the conductive system of the heart during depolarization, which causes a slowing of atrioventricular conductivity and increased effective refractive period of atrioventricular ganglia, which eventually leads to the relaxation of smooth muscle of heart musculature and restores normal sinus rhythm during supraventricular tachycardias. 

Atrial flutter Digitalis slows the heart normal sinus rhythm may appear. Often, flutter is converted to atrial fibrillation with a slow ventricular rate. 

Atrial fibrillation Peak digoxin body stores larger than the 8 to 12 mcg/kg required for most patients with heart failure and normal sinus rhythm have been used for control of ventricular rate in patients with atrial fibrillation. Titrate doses of digoxin used for the treatment of chronic atrial fibrillation to the minimum dose that achieves the desired ventricular rate control without causing undesirable side effects. Data are not available to establish the appropriate resting or exercise target rates that should be achieved. 

Rapid digitalization with a loading dose Peak digoxin body stores of 8 to 12 mcg/kg should provide therapeutic effect with minimum risk of toxicity in most patients with heart failure and normal sinus rhythm. Because of altered digoxin distribution and elimination, projected peak body stores for patients with renal insufficiency should be conservative (ie, 6 to 10 mcg/kg see Precautions). 

Atrial fibrillation is commonly associated with heart failure, and the prevalence of atrial fibrillation is related to the severity of heart failure, with less than 5% affected with very mild heart failure to nearly 50% affected with advanced heart failure [66]. Heart failure and atrial fibrillation are both common cardiovascular disorders and share the same demographic risk factors, including age, history of hypertension, prior myocardial infarction, and valvular heart disease [67, 68]. Further, the incidence of heart failure increases dramatically after the diagnosis of atrial fibrillation [69]. Progression of LV dysfunction can clearly be associated with rapid ventricular rates [70-76]. Conversely, conversion to normal sinus rhythm or control of ventricular response in atrial fibrillation can improve LV function [71-74, 77]. Accordingly, rate control becomes very important in patients with heart failure and dilated cardiomyopathy, and likely even more so when ischemia from rapid rates complicate the patient s course. 

Maintenance of normal sinus rhythm after conversion of atrial fibrillation or flutter, prevention of premature atrial, AV, and ventricular contractions paroxysmal atrial tachycardia paroxysmal AV functional rhythm atrial fibrillation atrial flatter paroxysmal ventricular tachycardia not associated with complete heart block PO 100-600 mg q4-6h. (Long-acting) 324-972 mg q8-12h. IV 200-400 mg. 

Low doses (100-200 mg/d) of amiodarone are effective in maintaining normal sinus rhythm in patients with atrial fibrillation. The drug is effective in the prevention of recurrent ventricular tachycardia. It is not associated with an increase in mortality in patients with coronary artery disease or heart failure. In many centers, the implanted cardioverter-defibrillator (ICD) has succeeded drug therapy as the primary treatment modality for ventricular tachycardia, but amiodarone may be used for ventricular tachycardia as adjuvant therapy to decrease the frequency of uncomfortable cardioverter-defibrillator discharges. The drug increases the pacing and defibrillation threshold and these devices require retesting after a maintenance dose has been achieved. 

Treatment of atrial fibrillation is initiated to relieve patient symptoms and prevent the complications of thromboembolism and tachycardia-induced heart failure, the result of prolonged uncontrolled heart rates. The initial treatment objective is control of the ventricular response. This is usually achieved by use of a calcium channel-blocking drug alone or in combination with a 13-adrenergic blocker. Digoxin may be of value in the presence of heart failure. A second objective is a restoration and maintenance of normal sinus rhythm. Several studies show that rate control (maintenance of ventricular rate in the range of 60-80 bpm) has a better benefit-to-risk outcome than rhythm control (conversion to normal sinus rhythm) in the long-term health of patients with atrial fibrillation. If rhythm control is deemed desirable, sinus rhythm is usually restored by DC cardioversion in the USA in... 

Digoxin is indicated in patients with heart failure and atrial fibrillation. It is also most helpful in patients with a dilated heart and third heart sound. It is usually given only when diuretics and ACE inhibitors have failed to control symptoms. Only about 50% of patients with normal sinus rhythm (usually those with documented systolic dysfunction) will have relief of heart failure from digitalis. Better results are obtained in patients with atrial fibrillation. If the decision is made to use a cardiac glycoside, digoxin is the one chosen in most cases (and the only one available in the USA). When symptoms are mild, slow loading (digitalization) with 0.125-0.25 mg per day is safer and just as effective as the rapid method (0.5-0.75 mg every 8 hours for three doses, followed by 0.125-0.25 mg per day). 

Patients with normal sinus rhythm and a wide QRS interval, eg, greater than 120 ms, have impaired synchronization of ventricular contraction. Poor synchronization of left ventricular contraction results in diminished cardiac output. Resynchronization, with left ventricular or biventricular pacing, has been shown to reduce mortality in patients with chronic heart failure who were already receiving optimal medical therapy. 

Peak body digoxin stores of 8 pg/kg to 12 pg/kg should provide therapeutic effect with minimum risk of toxicity for patients with heart failure and normal sinus rhythm... 

Quinidine is used for the maintenance of normal sinus rhythm in patients with atrial flutter or fibrillation. It is also used occasionally to treat patients with ventricular tachycardia. Because of its cardiac and extracardiac side effects, its use has decreased considerably in recent years and is now largely restricted to patients with normal (but arrhythmic) hearts. In randomized, controlled clinical trials, quinidine-treated patients are twice as likely to remain in normal sinus rhythm compared with controls. However, drug treatment was associated with a twofold to threefold increase in mortality. 

Cotter G, et al. Conversion of recent onset paroxysmal atrial fibrillation to normal sinus rhythm the effect of no treatment and high-dose amiodarone. A randomized, placebo-controlled study. Eur Heart J 1999 20(24) 1833-1842. 

For effectual rhythm control, the first action is often to restore NSR acutely with a nonsurgical intervention called a cardioversion, by which the patient s heart is reset through the use of electrical current strategically delivered to the heart via external electrode pads. When atrial fibrillation is changed to a normal sinus rhythm, the patient is said to have been converted. The cardioversion process has a good success rate for achieving conversion however, patients must be anesthetized for the procedure, and the AF often returns. 

Figure 12.3 Base-apex electrocardiograms from an 11 -year-old horse that presented in congestive heart failure, (a) Before treatment, with ventricular tachycardia (b) Conversion to normal sinus rhythm was achieved with 5 liters 0.64% solution quinidine giuconate, infused at approximately 1 l/h. No specific cause was identified, although echocardiography revealed a segmental area of hypomotile ventricular myocardium, suggestive of ischaemia. The horse was euthanased 3 weeks later after recurrence of the arrhythmia.

On the other hand, the medical condition where the heart beats too fast is known as tachycardia. If untreated, tliis condition may lead to ventricular fibrillation, that is, a condition in which the heart stops beating and shakes uncontrollably and is usually fatal. In 1980, a special device was developed and implanted in patients. It could sense the condition and provide a shock that would stop the fibrillation and restore the normal sinus rhythm via an electrode sutured onto the heart. The device was first powered by a lithium/vanadium pentoxide system later it was replaced by a system using a cathode material of silver vanadium oxide (SVO or Ag2V40ii). This is the actual system used in modem ICDs (implantable cardioverter/defibrillator). Another material used is the lithium/manganese dioxide system. Also, a new system using a sandwich cathode design with an inner cathode material of carbon monofluoride and an external cathode layer of silver vanadium oxide is in wide use. 

Slatton ML, Irani WN, Hall SA, et al. Does digoxin provide additional hemodynamic and autonomic benefits in patients with mild to moderate heart failure and normal sinus rhythm J Am Coll Cardiol 1997 29 1206-1213. 

AF atrial fibrillation CHF congestive heart failure ICD implantable cardioverter defibrillator LBBB left bundle branch block LVEDD left ventricular end diastolic dimension LVEF left ventricular ejection fraction 6MHWD 6-minute hall walk distance NSR normal sinus rhythm QoL quality of life TDI tissue Doppler imaging. 

CRT reduces symptoms of CHF and improves cardiac performance in patients with moderate-to-severely symptomatic heart failure, severe left ventricular systolic dysfunction, normal sinus rhythm and a wide QRS complex. Resynchronization therapy significantly reduces hospitalizations in these patients and is highly cost-effective. Perhaps most important, resynchronization therapy for heart failure improves survival for these patients, particularly when employed in conjunction with an implantable defibrillator. However, randomized clinical trials show that a substantial minority of patients are clinical nonresponders. Therefore, critical questions remain with respect to identifying appropriate candidates for CRT, optimal device programming, and left ventricular lead placement. 

Before discussing the various arrhythmias and the drugs used to treat them, it is advisable briefly to review a normal sinus rhythm and some of the electrical activities of the heart. 

Sotalol hydrochloride is a beta-adrenergic-blocking agent, which blocks beta receptors, which primarily affect heart (slows rate), vascular musculature (decreases BP), and lungs (reduces function). Betapace is used in the management or prevention of life-threatening ventricular arrhythmias. Betapace AT is used in the maintenance of normal sinus rhythm in patients with highly symptomatic atrial fibrilla-tion/atrial flutter (AFIB/AFL) (Betapace AF). 

Pharmacologic testing procedures for the cardioactive alkaloids pro- dde three types of information (1) alterations in the normal physiologic activities of the heart (2) conversion of artificial cardiac arrhythmias to normal sinus rhythm (3) compensation for the experimentally induced congestive heart failure. 

At this juncture it is worthwhile to have a little in-depth knowledge with regard to a normal sinus rhythm and aspects of the electrical characteristics of the heart. 

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