Conduction abnormalities

While the ECG is an invaluable tool for the observation of heart rate and rhythm, as well as for the diagnosis of conduction abnormalities, ischaemia, and infarcts, its detailed interpretation is not without pitfalls. One reason for this is that different changes in cardiac cellular behaviour may give rise to very similar effects on the ECG. This makes it difficult to draw conclusions from a patient s ECG to the underlying (sub-)cellular mechanisms. This issue is usually referred to as the inverse problem. ... 

Do not exceed a rate of 25 mg/min in elderly patients or in the presence of atherosclerotic heart disease or conduction abnormalities... 

Treatment with 3-blockers, verapamil, or diltiazem can usually be continued in patients with asymptomatic bradycardia. However, reduce or discontinue treatment with these agents in patients who develop symptomatic bradycardia or serious conduction abnormalities. 

However, there is a period of time following the absolute refractory period during which a premature electrical stimulus can be conducted, and is often conducted abnormally. This period of time is called the relative refractory period (Fig. 6-2).2 The relative refractory period corresponds roughly to the latter half of phase 3 repolarization on the action potential and to the latter half of the T wave on the ECG. If a new... 

Extra-articular involvement may include rheumatoid nodules, vasculitis, pleural effusions, pulmonary fibrosis, ocular manifestations, pericarditis, cardiac conduction abnormalities, bone marrow suppression, and lym-phadenopathy. 

Diltiazem and verapamil can cause cardiac conduction abnormalities such as bradycardia, AV block, and heart failure. Both can cause anorexia, nausea, peripheral edema, and hypotension. Verapamil causes constipation in about 7% of patients. 

Side effects from /1-blockade in the myocardium include bradycardia, AV conduction abnormalities, and acute heart failure. Blocking / -receptors in arteriolar smooth muscle may cause cold extremities and aggravate PAD or Raynaud s phenomenon because of decreased peripheral blood flow. 

Verapamil and diltiazem cause less peripheral vasodilation than dihydro-pyridines such as nifedipine but greater decreases in AV node conduction. They must be used with caution in patients with preexisting conduction abnormalities or in patients taking other drugs with negative chronotropic properties. 

The isolate is penicillin sensitive (MIC less than or equal to 0.1 mcg/mL). / There are no cardiovascular risk factors such as heart failure, aortic insufficiency, or conduction abnormalities. 

The Working Group on Status Epilepticus recommends that phenobar-bital be given after a BZ plus phenytoin has failed. Most practitioners agree that phenobarbital is the long-acting anticonvulsant of choice in patients with hypersensitivity to the hydantoins or in those with cardiac conduction abnormalities. 

Regulatory guidance for non-clinical cardiovascular safety pharmacology testing is given in the ICH S7A and B.25,42 The effects of an NCE on blood pressure, heart rate, and the ECG should be evaluated. Furthermore, in vivo, in vitro, and ex vivo evaluations, including methods for (assessing) repolarization and conductance abnormalities, should... 

The ICH guideline lists the assessment of effects on blood pressure, heart rate and ECG. In vivo, in vitro and/or ex vivo evaluations, including methods for electrical repolarisation and conductance abnormalities, should also be considered. These abnormalities can be associated with risks for fatal ventricular arrhythmias called Torsade de pointes. 

There are currently no subtle or sensitive biomarkers of effects associated with exposure to 2-hexanone. Electromyographic testing, however, may prove to be useful in the detection of nerve conduction abnormalities in their early stages, even before they are accompanied by clinical manifestations. Specific electrodiagnostic patterns associated with exposure to 2-hexanone have not been clearly delineated. 

Conduction abnormalities Use caution in patients with sick sinus syndrome, Wolff-Parkinson-White syndrome or bundle branch block. 

Cardiovascular effects If a ventricular pacemaker is operative, patients with seconder third-degree heart block may be treated with mexiletine if continuously monitored. Exercise caution in such patients or in patients with preexisting sinus node dysfunction or intraventricular conduction abnormalities. 

Concomitant therapy Concomitant therapy with -blockers or digitalis is usually well tolerated, but the effects of coadministration cannot be predicted, especially in patients with left ventricular dysfunction or cardiac conduction abnormalities. 

Concomitant use of calcium channel blockers (atenolol) Bradycardia and heart block can occur and the left ventricular end diastolic pressure can rise when beta-blockers are administered with verapamil or diltiazem. Patients with preexisting conduction abnormalities or left ventricular dysfunction are particularly susceptible. Recent acute Ml (sotalol) Sotalol can be used safely and effectively in the long-term treatment of life-threatening ventricular arrhythmias following an Ml. However, experience in the use of sotalol to treat cardiac arrhythmias in the early phase of recovery from acute Ml is limited and at least at high initial doses is not reassuring. 

Uses Rx prevent osteoporosis male female, Rx steroid-induced osteoporosis, Paget Dz Action -1- N1 abnormal bone resorption Dose Osteoporosis Rx 10 mg/d PO or 70 mg qwk Fosamax plus D 1 tab qwk Steroid-induced osteoporosis Rx 5 mg/d PO Prevention 5 mg/d PO or 35 mg qwk Paget Dz 40 mg/d PO Caution [C, ] Not OK if CrCl <35 mLAnin, w/ NSAID use Contra Esophageal anomalies, inability to sit/stand upright for 30 min, X Ca Disp Tabs, soln SE GI disturbances, esophageal irritation, HA, pain, jaw osteonecrosis (w/ dental procedures, chemo) Interactions -1- Absorption W7 antacids, Ca supls, Fe, food T risk of upper GI bleed W/ ASA NSAIDs EMS May cause cardiac conduction abnormalities d/t T Ca T risk of jaw fractures esp w/ dental procedures OD May cause hypocalcemia and adverse upper-GI effects milk or antacids can be given to bind alendronate... 

Ca, leg cramps EMS May cause cardiac conduction abnormalities d/t T monitor ECG not used to prevent osteoporosis osteosarcoma has been rqwrted in animals OD May cause NA, HA, and h5 percalcemia and associated cardiac conduction problems s5rmptomatic and supportive... 

Conduction system abnormalities are common in chronic heart failure, occurring in 15-30% of the population with low left ventricular ejection fraction (LVEF) [1-3]. The prevalence in ischemic heart disease is roughly similar to that seen in other forms of dilated cardiomyopathy. Conduction system disease can occur both at the time of an acute myocardial infarction as well as slowly progressing in chronic ischemic heart disease. Intraventricular conduction delays are associated with a poor prognosis in heart failure, with up to a 70% increase in the risk of death, and are also more prevalent in patients with advanced symptoms [2,4]. In ischemic heart disease, all components of the conduction system are at risk of ischemic injury, from the sinoatrial node to the His-Pukinje system. These conduction system abnormalities have the potential to impair cardiac function by a number of mechanisms. Since conduction abnormalities impair cardiac function, it is logical that pacing therapies to correct or improve these conduction abnormalities may improve cardiac function. 

Although much of the data regarding the frequency of conduction abnormalities during acute myocardial infarction were derived from studies prior to the era of rapid reperfusion [14 17], data from more recent trials suggest that the incidence of intraventricular conduction defects has changed very little. 

A series of pilot studies began with multisite pacing for patients with heart failure and dilated cardiomyopathy in the early 1990s [52, 105-111]. An improvement in LV function and symptoms of heart failure were demonstrated. This provided the interest in biventricular pacing for heart failure. The term cardiac resynchronization therapy was coined to refer to pacing therapies that attempt to enhance cardiac performance by using pacing to correct electrical conduction abnormalities in the heart. The most common form of this therapy is atrial-synchronous... 

Appleton CP, Basnight MA, Gonzalez MS. Diastolic mitral regurgitation with atrioventricular conduction abnormalities relation of mitral flow velocity to transmittal pressure gradients in conscious dogs. J. Am. Coll. Cardiol. 1991 18 843-9. 

Ventricular arrhythmias, including ventricular tachycardia, atrial fibrillation, node conduction abnormalities, and angina pectoris, occur rarely. 

In the case of abnormal EKGs at baseline, the use of a TCA, as well as potential risks and benefits, needs to be carefully reevaluated. In addition, a family history of premature cardiac problems or a personal history of cardiac disease, especially structural and conduction abnormalities, should warrant consultation with a pediatric cardiologist before starting medications. Parents and patients should be aware of the potential risk for... 

Trazodone overdose carries a risk of myocardial irritation in patients with preexisting ventricular conduction abnormalities. 

Circulatory failure (decreased blood pressure, cardiac arrhythmias, conduction abnormalities)... 

Although b-blockers are considered the treatment of choice for akathisia, low doses of clonazepam, diazepam, or lorazepam may also reduce its severity ( 172, 389, 445, 447, 448, 449 and 450). These BZDs may be a useful alternative when a-blockers are contraindicated (e.g., in patients with asthma, insulin-dependent diabetes meilitus, cardiac conduction abnormalities) or as an adjunct when akathisia persists despite stepwise escalation of these agents ( 177). 

The pharmacokinetic properties of these drugs are set forth in Table 12-5. The choice of a particular calcium channel-blocking agent should be made with knowledge of its specific potential adverse effects as well as its pharmacologic properties. Nifedipine does not decrease atrioventricular conduction and therefore can be used more safely than verapamil or diltiazem in the presence of atrioventricular conduction abnormalities. A combination of verapamil or diltiazem with 3 blockers may produce atrioventricular block and depression of ventricular function. In the presence of overt heart failure, all calcium channel blockers can cause further worsening of heart failure as a result of their negative inotropic effect. Amlodipine, however, does not increase the mortality of patients with heart failure due to nonischemic left ventricular systolic dysfunction and can be used safely in these patients. 

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