Sinus bradycardia causes

Numerous drugs ((1-blockers, diltiazem, verapamil, digoxin, and amiodarone) can cause bradyarrhythmias (sinus bradycardia and AV nodal blockade). 

Many individuals, particularly those who partake in regular vigorous exercise, have heart rates less than 60 bpm. For those individuals, sinus bradycardia is normal and healthy, and does not require evaluation or treatment. However, some individuals develop symptomatic sinus node dysfunction. In the absence of correctable underlying causes, idiopathic sinus node dysfunction is referred to as sick sinus syndrome,12 and occurs with greater frequency with advancing age. The prevalence of sick sinus syndrome is approximately 1 in 600 individuals over the age of 65 years.12... 

Sick sinus syndrome leading to sinus bradycardia may be caused by degenerative changes in the sinus node that occur with advancing age. However, there are other possible etiologies of sinus bradycardia, including drugs (Table 6-2).13... 

Determine whether the patient is taking any drugs known to cause sinus bradycardia. If the patient is currently taking digoxin, determine the serum digoxin concentration and ascertain whether it is supratherapeutic (greater than 2 ng/mL [2.56 nmol/L]). 

Treatment of sinus bradycardia is only necessary in patients who become symptomatic. If the patient is taking any med-ication(s) that may cause sinus bradycardia, the drug(s) should be discontinued whenever possible. If the patient remains in sinus bradycardia after discontinuation of the drug(s) and after five half-lives of the drug(s) have elapsed, then the drugs(s) can usually be excluded as the etiology of the arrhythmia. In certain circumstances, however, discontinuation of the medication(s) may be undesirable, even if it may be the cause of symptomatic sinus bradycardia. For example, if the patient has a history of myocardial infarction or HF, discontinuation of a (3-blocker is undesirable, because (3-blockers have been shown to reduce mortality and prolong life in patients with those diseases, and the benefits of therapy with... 

Blockers are contraindicated in patients with decompensated heart failure unless it is caused solely by tachycardia (high output). Other contraindications include sinus bradycardia, concomitant therapy with monoamine oxidase inhibitors or tricyclic antidepressants, and patients with spontaneous hypoglycemia. Side effects include nausea, vomiting, anxiety, insomnia, lightheadedness, bradycardia, and hematologic disturbances. 

Sinus node disease andAVbiock The drug may cause severe sinus bradycardia or sinoatrial block in patients with preexisting sinus node disease and may cause advanced or complete heart block in patients with preexisting incomplete AV block. Consider inserting a pacemaker before treatment with digoxin. 

Sick sinus syndrome Use only with extreme caution the drug may cause sinus bradycardia, sinus pause, or sinus arrest. The frequency probably increases with higher trough plasma levels. 

Oral Severe sinus-node dysfunction, causing marked sinus bradycardia second-and third-degree AV block when episodes of bradycardia have caused syncope (except when used in conjunction with a pacemaker). 

Sinus rhythm with a rate of less than 60/min is defined as sinus bradycardia. This bradycardia is usually a physiological response. Pathological and/or symptomatic sinus bradycardia may suggest sinus node dysfunction (see sick sinus syndrome). Vagally induced sinus bradycardia may be responsive to atropine, but only needs to be treated if symptomatic. Atropine doses of less than 0.5 mg may cause a paradoxical increase in vagal bradycardia. 

Atropine can be used in the differential diagnosis of S-A node dysfunction. If sinus bradycardia is due to extracardiac causes, atropine can generally elicit a tachy-cardic response, whereas it cannot elicit tachycardia if the bradycardia results from intrinsic causes. Under certain conditions, atropine may be useful in the treatment of acute myocardial infarction. Bradycardia frequently occurs after acute myocardial infarction, especially in the first few hours, and this probably results from excessive vagal tone. The increased tone and bradycardia... 

Depression or cardiac excitability and contractility may cause AV block, ventricular arrhythmias, or cardiac arrest. Symptoms of local anesthetic CNS toxicity, such as dizziness, tongue numbness, visual impairment or disturbances, and muscular twitching appear to occur before cardiotoxiceffects. Cardiotoxic effects include angina, QT prolongation, PR prolongation, atrial fibrillation, sinus bradycardia, hypotension, palpitations, and cardiovascular collapse. 

Vomiting is common in patients with digitalis overdose. Hyperkalemia may be caused by acute digitalis overdose or severe poisoning, whereas hypokalemia may be present in patients as a result of long-term diuretic treatment. (Digitalis does not cause hypokalemia.) A variety of cardiac rhythm disturbances may occur, including sinus bradycardia, AV block, atrial tachycardia with block, accelerated junctional rhythm, premature ventricular beats, bidirectional ventricular tachycardia, and other ventricular arrhythmias. 

Caution [C, ] CrCl <30 Contra Component sensitivity, asthma, severe COPD, sinus bradycardia Disp Soln SE Irritation, bitter taste, superficial keratitis, ocular allergic Rxn EMS Drug is absorbed systemically OD May cause electrolyte disturbances (K), acidosis and bradycardia monitor ECG Doxazosin (Cardura, Cardura XL) [Antihypertensive/Alpha Blocker] Uses HTN symptomatic BPH Action < [-Adrenergic blocker relaxes bladder neck smooth muscle Dose HTN Initial 1 mg/d PO may be T to 16 mg/d PO BPH Initial 1 mg/d PO, may T to 8 mg/d XR 2-8mg qAM Caution [B, ] Use w/ PDE5 inhibitor (eg, sildenafil) can cause 1 BP Contra Component sensitivity Disp Tabs SE Dizziness, HA, drowsiness, sexual dysfxn, doses >4 mg T postural BP risk Interactions T Effects W/ nitrates, antihypertensives, EtOH i effects W/ NSAEDs, butcher s broom -t effects OF clonidine EMS Concurrent EtOH use can T drowsiness syncope may occur w/in 90 min of initial dose OD May cause profound hypotension place pt in supine position, give IV fluids, use pressors if needed... 

Succinylcholine may cause tachycardia, cardiac arrhythmias, and hypertension, which is brought about by stimulation of the sympathetic ganglia. It may also provoke bradycardia, caused by stimulation of muscarinic receptor sites in the sinus node of the heart. This effect is more pronounced following a second dose of succinylcholine. The bradycardia may be blocked by thiopental, atropine, and ganglionic blocking agents. 

Rothenhausler HB, Hoberl C, Ehrentrout S, Kapfhammer HP, Weber MM. Suicide attempt by pure citalopram overdose causing long-lasting severe sinus bradycardia, hypotension and syncopes successful therapy with a temporary pacemaker. Pharmacopsychiatry 2000 33(4) 150-2. 

In terms of its potential for inducing cardiac dysrhythmias, cannabis is most likely to cause palpitation due to a dose-related sinus tachycardia. Other reported dysrhythmias include sinus bradycardia, second-degree atrioventricular block, and atrial fibrillation. Also reported are ventricular extra beats and other reversible electrocardiographic changes. 

Although betaxolol generally elicits less systemic beta-blockade than do noncardioselective agents, it does cause undesirable systemic effects in some patients. Reported adverse experiences include congestive heart failure, myocardial infarction, respiratory difficulties strongly suggestive of obstructive airway disease, weakness with severe sinus bradycardia, and wheezing with objective reduction in pulmonary function. 

Adverse effects include nausea, dizziness, disturbance of balance, vomiting, abdominal pain, diarrhoea and loss of appetite. More rarely, hallucinations, seizures and psychoses occur. Mefloquine should be avoided in patients taking (i-adrenoceptor and calcium channel antagonists for it causes sinus bradycardia quinine can potentiate these and other... 

The most common cardiac effects are atrioventricular block, sinus bradycardia, and ventricular extra beats. Occasionally serious dysrhythmias occur (SEDA-17, 219), including ventricular fibrillation (15). ATP can cause transient atrial fibrillation (16). Chest pain occurs in 30-50% of patients and dyspnea and chest discomfort in 35-55%. Chest pain can occur in patients with and without coronary artery disease, and the symptoms are not always tjrpical of cardiac pain. 

Patients with impaired function of the sinus node or impaired atrioventricular conduction can develop sinus bradycardia, sinus arrest, heart block, hypotension and shock, and even asystole, with verapamil (139) or diltiazem. These drugs should not be given to patients with aberrant conduction pathways associated with broad-complex tachydysrhythmias, and they can cause severe conduction disturbances in hypertrophic cardiomyopathy. 

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. 

The combination of disopjramide and practoioi can cause profound sinus bradycardia and asystole (40,41). 

Lidocaine can cause dysrhythmias and hypotension. The dysrhythmias that have been reported include sinus bradycardia, supraventricular tachycardia (11), and rarely torsade de pointes (12). There have also been rare reports of cardiac arrest (2) and worsening heart failure (13). Lidocaine can also cause an increased risk of asystole after repeated attempts at defibrillation (14). Lidocaine may increase mortality after acute myocardial infarction, and it should be used only in patients with specific so-called warning dysrhythmias (that is frequent or multifocal ventricular extra beats, or salvos) (15). 

Most side effects of the calcium channel blockers are related to their mechanism of action. Verapamil and diltiazem can both cause sinus bradycardia and may worsen CHF. Constipation has been associated with verapamil use. The dihydropyridines often cause symptoms associated with vasodilatation, such as facial flushing, peripheral edema, hypotension, and headache. Because dihydropyridines are potent vasodilators, they can cause reflex tachycardia, which may precipitate palpitations, worsening angina, or Ml. Lastly, all calcium channel blockers can cause Gl complaints and fatigue. 

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