Special Clinical ECG Syndromes

Sick sinus syndrome (SSS) is a group of electrocardiographic and clinical findings. Patients often have symptoms of fatigue, palpitations, and heart racing and may suffer from dizzy spells or even syncope. The findings of paroxysmal atrial tachycardia, atrial fibrillation (AF), or atrial flutter result in tachypalpitations and heart racing. Excessive SA

node suppression often occurs with drugs used to slow AV conduction or reduce atrial arrhythmias. Figure 27-51 demonstrates typical ECG findings seen in SSS. Pharmacologic treatment to reduce symptoms is often problematic, and permanent pacing is often required. Anticoagulation with warfarin in patients with documented AF should be considered. Patients without documented AF should be considered for aspirin anticoagulation because of the high frequency of asymptomatic AF in this patient population (Myerbaurg, 1994).

There are at least two types of supraventricular tachycardia (SVT) that should be routinely considered for referral. Patients with preexcitation syndrome (Wolfe-Parkinson-White, WPW) or atrioventricular reciprocating tachycardia (AVRT) and paroxysmal, symptomatic atrioventricular node reentrant tachycardia (AVNRT) may benefit from drug therapy or RF ablation therapy. The ECG signature of WPW is the delta wave. Atrial activation of the ventricle is through the AV node-Purkinje system and is activated through a bundle or bypass tract of muscle inserting along one of the AV valves. The combined activation pattern results in the delta wave. Figures 27-52 and 27-53 demonstrate presence and absence of the delta

Data Ok

Data Ok

Invalid

Data Ok

Invalid

02:10:51> VWVVHV NVAwVvw* 02:11:21> VWMMA

Data Ok

MWVMWVVHvWHVVVWVV^^

Invalid nvalid Data Ok

Figure 27-49 Sinus rhythm is noted to degrade initially to a polymorphic ventricular tachycardia and then organizes for about minutes (not shown in entirety). A premature ventricular contraction during ventricular tachycardia results in ventricular fibrillation, to which the patient ultimately succumbed.

Figure 27-50 Dual-chamber pacing with loss of ventricular output.

Figure 27-50 Dual-chamber pacing with loss of ventricular output.

Figure 27-51 Sick sinus syndrome is ch laracterized by rapidly conducted atrial fibrillation, pauses during restoration or sinus rhythm, and excessive bradycardia in normal rhythm.

wave before and after RF therapy for SVT associated with the bypass tract. SVT results from a macroreentrant circuit where conduction proceeds down the AV node into the ventricular myocardium and retrograde up the bypass tract to activate the atrium. The circuit is completed as the AV node is again activated. Tachycardias moving in the opposite direction are identified as wide QRS tachycardias and may be indistinguishable from VT by surface ECG. Adenosine administration during tachycardia may terminate WPW tachycardia but is unlikely to terminate VT. Caution to avoid hypotension or ventricular fibrillation during diagnostic atropine administration in nonhypotensive wide-complex tachycardia is recommended. Advanced cardiac life support equipment should be available during administration.

Sudden, rapid onset and offset of narrow-complex tachycardia occurs in AVNRT. Either an inverted P wave immediately follows the QRS complex, or it may not be visible at all. Termination of the arrhythmia using vagal maneuvers (e.g., carotid sinus massage, Valsalva, stimulation with ice-cold water) may be used clinically. Treatment with AV node-blocking agents can be successful in most patients. Safe, highly effective treatment with invasive electrophysiol-ogy study and RF therapy is common at most larger centers. Figures 27-53 and 27-54 illustrate the mechanism and ECG findings.

Long QT syndrome, a disorder of myocardial repolariza-tion, results from abnormalities in membrane ion channels. Syncope and life-threatening polymorphous VT and VF may result. Autosomal dominant inheritance patterns and variable phenotypic penetrance may be seen. Diagnosis in affected individuals is difficult because the QT interval may occasionally be normal. Provocative maneuvers by a trained specialist may be necessary. Genetic testing for some but not all of the genetic abnormalities is available for confirmation.

Figure 27-52 Sinus rhythm with obvious delta waves consistent with a right-sided septal or posteroseptal origin. Twelve-lead electrocardiography is performed before radiofrequency ablation.

Figure 27-53 Normal electrocardiogram following radiofrequency ablation of the manifest right posteroseptal bypass tract.

Families with a history of sudden cardiac death or syncope should be evaluated carefully to determine the need for treatment, including beta blockers and implantable defibrillators (Priori et al., 2003).

Atrial fibrillation is the most frequent arrhythmia requiring treatment. In America, 2.2 million people have persistent or permanent AF (Feinberg et al., 1997). A basic understanding to the approach of AF can render most patients asymptomatic and dramatically reduce their risk of stroke. The AFFIRM trial represents a landmark study treating all AF patients with warfarin (Coumadin). Patients were then randomized to either (1) control of heart rate utilizing AV nodal blocking agents, or if necessary, AV junction ablation and pacemaker therapy, or (2) maintenance of sinus rhythm utilizing antiarrhythmic drug therapy and repeated direct-current (DC) cardioversion. Patients were followed for up to 5 years and had similar mortality. Patients randomized to rhythm control had more hospitalizations and adverse drug effects, mostly related to antiarrhythmic therapy. Stroke events were similar but were higher in patients who discontinued warfarin, regardless of treatment arm (AFFIRM Investigators, 2002). Based on this study, patients who are candidates for either heart rate control or rhythm control can pursue either treatment strategy with similar efficacy. In patients undergoing restoration of sinus rhythm, the use of DC cardioversion is safe and effective. Anticoagulation with an INR goal of 2 to 3 in nonvalvular AF is recommended for a minimum of 3 weeks before a cardioversion.

Conscious sedation with short-acting narcotics and intravenous benzodiazepines allows for synchronized shock delivery in ASA class I and II patients by experienced physicians. In patients adequately anticoagulated with warfarin, DC cardioversion can restore sinus rhythm at least transiently in 70% to 90% of patients (Lundstrom and Ryden, 1988; Sodermark et al., 1975; Van Gelder et al., 1991). Maintenance of sinus rhythm at 12 months on antiarrhythmic medications may be as low as 40% depending on drug selection and the patient population (Van Gelder et al., 1996). Despite this, the practicing physician may elect to gain expertise in conscious sedation and cardioversion when referral electrophysiologists are not readily available and in patients not requiring or intolerant to drug therapy. Prior recommendations for discontinuation of warfarin after 6 weeks in sinus rhythm (SR) are being scrutinized because of the high stroke rate in patients in the AFFIRM trial that discontinued warfarin despite being in SR. Caregivers may treat patients long

Figure 27-54 Sinus rhythm is noted in the upper strip. In the lower panel, supraventricular tachycardia consistent with atrioventricular nodal reentrant tachycardia is seen. Retrograde (inverted) P waves immediately following the QRS complex during tachycardia are evident. During the tachycardia at almost 150 beats/min, the normal P-R interval is no longer seen.

Figure 27-54 Sinus rhythm is noted in the upper strip. In the lower panel, supraventricular tachycardia consistent with atrioventricular nodal reentrant tachycardia is seen. Retrograde (inverted) P waves immediately following the QRS complex during tachycardia are evident. During the tachycardia at almost 150 beats/min, the normal P-R interval is no longer seen.

term, even after SR is restored, or in patients with asymptomatic AF. Because of the high 6-month recurrence rate after cardioversion, many maintain patients on anticoagulation for 6 or more months before considering stopping it. Recommendations for anticoagulation are certain to change as new drugs become available.

Syncope is the sudden loss of postural tone and may be caused by both cardiac and noncardiac causes; up to 30% of patients may ultimately have no explanation. A detailed history that includes dietary and fluid intake, personal and family history, medication use and timing, and precipitating factors will aid in the diagnosis. The best single determinant of an etiology is likely the history. Additional testing depends on the presence or absence of structural heart disease. Invasive electrophysiology study in the setting of structural heart disease may identify the cause of syncope in up to one half of patients (Linzer et al., 1997). In the absence of structural heart disease, tilt-table testing may identify the cause in 11% to 87% of patients (Kapoor, 1990, 1992). Referral to an elec-trophysiologist should be considered in the setting of structural heart disease.

Stop Anxiety Attacks

Stop Anxiety Attacks

Here's How You Could End Anxiety and Panic Attacks For Good Prevent Anxiety in Your Golden Years Without Harmful Prescription Drugs. If You Give Me 15 minutes, I Will Show You a Breakthrough That Will Change The Way You Think About Anxiety and Panic Attacks Forever! If you are still suffering because your doctor can't help you, here's some great news...!

Get My Free Ebook


Post a comment