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Atypical right atrial flutter patterns
Arrhythmias
Methods: Electropharmacologic testing was performed in 330 randomized to receive antiarrhythmic therapy. Programmed ventricular stimulation was performed at 2 right ventricular sites with up to 3 extrastimuli. The drugs used in MUSTT consisted of quinidine, disopyramide, procainamide, propafenone, sotalol and amiodarone. Drug therapy was considered effective if it rendered VT noninducible or inducible but hemodynamically stable. Results: An effective drug regimen was identified in 142 patients of 330 patients (43%) randomized to antiarrhythmic therapy. VT was noninducible in 91 patients and stable in 51 patients. Survival was approximately 70% at 2 years and did not differ between patients treated with an effective drug regimen and 353 patients randomized to receive no antiarrhythmic therapy. There also was no difference in survival between patients without inducible VT and those with inducible but stable VT. Survival appeared to be greater with sotalol than with propafenone, but this trend was not confirmed statistically. Conclusions: Whether the end point is noninducibility of VT or stable VT, drug regimens found to be effective by electropharmacologic testing offer no survival benefit to patients with coronary artery disease, an EF ⱕ0.40, nonsustained VT and inducible sustained VT. Perspective: MUSTT was limited to patients with nonsustained ventricular tachycardia, but it is logical to assume that the results would be similar in patients with sustained VT. Because a trial in which patients with sustained ventricular tachycardia/fibrillation are randomized to no antiarrhythmic therapy is ethically impossible, there probably will never be any data that come closer to demonstrating the absence of any survival advantage of drug therapy guided by electrophysiologic testing in patients with sustained VT. FM
Abstracts Cardiac Arrest in Medical and Dental Practices. Implications for Automated External Defibrillators Becker L, Eisenberg M, Fahrenbruch C, Cobb L. Arch Intern Med 2001;161:1509 –12. Study Question: What is the incidence of cardiac arrest in community medical and dental practices in Seattle and King County, Washington? Methods: Emergency medical service records from 1990 through 1996 were reviewed to identify cardiac arrests requiring defibrillation or cardiopulmonary resuscitation that occurred in a dialysis center, urgent care center, community-based cardiology practice, family or internal medicine practice, all other medical specialty practices or in a dental practice. Demographic characteristics of the patients were recorded, as were their outcomes. Results: One hundred forty-two cardiac arrests that occurred in a medical or dental practice were identified. These represented 2% of all cardiac arrests in Seattle and King County. Survival to discharge from the hospital was 34%. The annual incidence of cardiac arrest per practice was 0.75 for dialysis centers, 0.03– 0.04 for cardiology practices and urgent care centers, 0.01 for internal and family medicine practices and 0.001– 0.002 for all other medical practices and dental practices. Conclusions: It is appropriate to place an automatic external defibrillator (AED) in community-based practices where there is a high or medium incidence of cardiac arrest. These sites consist of dialysis centers, cardiology practices, urgent care centers and internal and family medicine practices. Perspective: This study provides data that can be used to maximize the cost-effectiveness of AEDs in community practices. However, whether the placement of an AED in the practices that have the highest incidences of cardiac arrest will result in an improvement in survival to hospital discharge from the current level of 34% remains to be determined. FM
Atypical Right Atrial Flutter Patterns Yang Y, Cheng J, Bochoeyer A, et al. Circulation 2001;103:3092– 8. Study Question: What are the mechanisms of atypical atrial flutter (AFl) arising in the right atrium? Methods: Activation and entrainment mapping were performed in 372 consecutive patients referred for catheter ablation of AFl. Atypical AFl was defined as AFl other than typical counterclockwise or clockwise AFl utilizing the cavotricuspid isthmus. Among the 372 patients, 88% were found to have typical isthmus-dependent AFl, and 4% were found to have AFl arising in the left atrium. Thirty-six episodes of atypical right AFl were found in 28 patients (8%). Six of the patients had structural heart disease, but none had an atriotomy. Results: In 24 episodes of atypical right AFl in 15 patients (54%), the mechanism was found to be lower loop reentry, a reentrant circuit in the lower portion of the right atrium that utilized the cavotricuspid isthmus. In 4 of 28 patients (14%), there was counterclockwise reentry that utilized the
Antiarrhythmic Drug Therapy in the Multicenter UnSustained Tachycardia Trial (MUSTT): Drug Testing and As-Treated Analysis Wyse DG, Talajic M, Hafley GE, et al. J Am Coll Cardiol 2001;38: 344 –51. Study Question: The results of MUSTT originally were analyzed on an intention-to-treat basis, and antiarrhythmic drug therapy was found to confer no survival advantage to patients with coronary artery disease (CAD), an ejection fraction (EF) ⱕ0.40, nonsustained ventricular tachycardia (VT) and inducible VT. This study reanalyzed the results of MUSTT using an as-treated analysis.
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cavotricuspid isthmus and short-circuited the eustachian ridge barrier. Eight episodes in 7 patients (25%) were determined to be caused by upper loop reentry, a reentrant circuit involving the upper portion of the right atrium and not utilizing the cavotricuspid isthmus. Finally, in 2 patients (7%), there was reentry around areas of scar in the posterolateral right atrium. Conclusions: Mechanisms of flutter that are dependent on the cavotricuspid isthmus are present in approximately two-thirds of patients with atypical right AFl. Non-isthmusdependent mechanisms of flutter are present in approximately one-third of patients with atypical right AFl. Perspective: The results of this study imply that a majority of atypical right AFls can be successfully ablated by the conventional technique of creating block in the cavotricuspid isthmus. The right AFls that are not isthmusdependent are more challenging to ablate, but account for only approximately 2% of patients referred for ablation of AFl. FM
have AVNRT or AVRT. However, false negative ATP tests are common. Perspective: ATP is not available in the United States, but it is likely that similar results can be achieved with adenosine at a starting dose of 6 mg, with repeated injections in 6 mg increments until one of the end points of the ATP test is reached. However, the clinical value of this type of testing is limited since a patient with rapid palpitations often may have AVNRT or AVRT despite a negative bedside test. FM
Value of Programmed Ventricular Stimulation for Prophylactic Internal Cardioverter-Defibrillator Implantation in Postinfarction Patients Preselected by Noninvasive Risk Stratifiers Schmitt C, Barthel P, Ndrepepa G, et al. J Am Coll Cardiol 2001;37:1901–7. Study Question: Can a combination of noninvasive tests and programmed ventricular stimulation (PVS) shortly after a myocardial infarction (MI) identify high-risk patients who benefit from an internal cardioverter-defibrillator (ICD)? Methods: Noninvasive evaluation of ejection fraction (EF), ventricular ectopy, heart rate variability and late potentials was performed in 1436 patients with an acute MI. Based on this assessment, 194 patients who were ⱕ75 years in age were identified as being high-risk and advised to undergo PVS. Ninety-eight of these 194 patients consented to PVS, which was performed a median of 18 days post-MI. An ICD was implanted if sustained, monomorphic ventricular tachycardia (VT) was inducible by PVS. Results: Sustained, monomorphic VT was induced in 21 of 98 patients who underwent PVS, and an ICD was implanted in 20 of these patients. During a mean follow-up of approximately 600 days, sudden death, VT or cardiac arrest occurred in 33% of patients with a positive response to PVS, compared to 2.6% with a negative response (p⬍0.001). Cardiac mortality was 4.7 times more likely in the high-risk patients who declined PVS than in those who underwent PVS. Conclusion: A combination of noninvasive testing and PVS identifies high-risk patients who benefit from prophylactic implantation of an ICD after an acute MI. Perspective: The patients in this study overlap with the patients included in prior post-infarction trials (MUSTT and MADIT) that have demonstrated the ICD to have a beneficial effect on survival, and the results therefore are not surprising. A notable difference is that a low EF plus nonsustained VT were required for entry into MUSTT and MADIT, while in the present study, simply a low EF was sufficient for a patient to undergo PVS. However, largerscale studies are needed before PVS can be recommended in post-MI patients with a low ejection fraction who do not have nonsustained VT. FM
The Adenosine Triphosphate Test: A Bedside Diagnostic Tool for Identifying the Mechanism of Supraventricular Tachycardia in Patients With Palpitations Viskin S, Fish R, Glick A, Glikson M, Eldar M, Belhassen B. J Am Coll Cardiol 2001;38:173–7. Study Question: Prior studies have demonstrated that injection of adenosine triphosphate (ATP) can uncover evidence of dual atrioventricular nodal pathways or a concealed accessory pathway. The purpose of this study was to determine how often the ATP test identifies patients with palpitations who have atrioventricular nodal reentrant tachycardia (AVNRT) or atrioventricular reentrant tachycardia (AVRT). Methods: A history of rapid palpitations of sudden onset was present in 140 patients in whom tachycardia either was undocumented or documented but of unclear mechanism. These patients underwent an ATP test followed by an electrophysiology test. ATP was administered intravenously during sinus rhythm at the bedside at an initial dose of 10 mg, with repeated injections in 10 mg increments until an end point was reached. The ATP test was positive when it revealed dual atrioventricular nodal physiology or atrioventricular reentrant echo beats. The test was negative when high-degree atrioventricular block occurred without any positive findings. Results: The ATP test was positive in 63% of patients and negative in 37%. The sensitivity of a positive ATP test for AVNRT or AVRT was 71%, with a positive predictive value of 93%. A negative ATP test had a specificity of 76%, with a negative predictive value of 37%. Conclusions: A positive ATP test is helpful in predicting which patients with palpitations of unclear mechanism
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Methods: Electropharmacologic testing was performed in 330 randomized to receive antiarrhythmic therapy. Programmed ventricular stimulation was performed at 2 right ventricular sites with up to 3 extrastimuli. The drugs used in MUSTT consisted of quinidine, disopyramide, procainamide, propafenone, sotalol and amiodarone. Drug therapy was considered effective if it rendered VT noninducible or inducible but hemodynamically stable. Results: An effective drug regimen was identified in 142 patients of 330 patients (43%) randomized to antiarrhythmic therapy. VT was noninducible in 91 patients and stable in 51 patients. Survival was approximately 70% at 2 years and did not differ between patients treated with an effective drug regimen and 353 patients randomized to receive no antiarrhythmic therapy. There also was no difference in survival between patients without inducible VT and those with inducible but stable VT. Survival appeared to be greater with sotalol than with propafenone, but this trend was not confirmed statistically. Conclusions: Whether the end point is noninducibility of VT or stable VT, drug regimens found to be effective by electropharmacologic testing offer no survival benefit to patients with coronary artery disease, an EF ⱕ0.40, nonsustained VT and inducible sustained VT. Perspective: MUSTT was limited to patients with nonsustained ventricular tachycardia, but it is logical to assume that the results would be similar in patients with sustained VT. Because a trial in which patients with sustained ventricular tachycardia/fibrillation are randomized to no antiarrhythmic therapy is ethically impossible, there probably will never be any data that come closer to demonstrating the absence of any survival advantage of drug therapy guided by electrophysiologic testing in patients with sustained VT. FM
Abstracts Cardiac Arrest in Medical and Dental Practices. Implications for Automated External Defibrillators Becker L, Eisenberg M, Fahrenbruch C, Cobb L. Arch Intern Med 2001;161:1509 –12. Study Question: What is the incidence of cardiac arrest in community medical and dental practices in Seattle and King County, Washington? Methods: Emergency medical service records from 1990 through 1996 were reviewed to identify cardiac arrests requiring defibrillation or cardiopulmonary resuscitation that occurred in a dialysis center, urgent care center, community-based cardiology practice, family or internal medicine practice, all other medical specialty practices or in a dental practice. Demographic characteristics of the patients were recorded, as were their outcomes. Results: One hundred forty-two cardiac arrests that occurred in a medical or dental practice were identified. These represented 2% of all cardiac arrests in Seattle and King County. Survival to discharge from the hospital was 34%. The annual incidence of cardiac arrest per practice was 0.75 for dialysis centers, 0.03– 0.04 for cardiology practices and urgent care centers, 0.01 for internal and family medicine practices and 0.001– 0.002 for all other medical practices and dental practices. Conclusions: It is appropriate to place an automatic external defibrillator (AED) in community-based practices where there is a high or medium incidence of cardiac arrest. These sites consist of dialysis centers, cardiology practices, urgent care centers and internal and family medicine practices. Perspective: This study provides data that can be used to maximize the cost-effectiveness of AEDs in community practices. However, whether the placement of an AED in the practices that have the highest incidences of cardiac arrest will result in an improvement in survival to hospital discharge from the current level of 34% remains to be determined. FM
Atypical Right Atrial Flutter Patterns Yang Y, Cheng J, Bochoeyer A, et al. Circulation 2001;103:3092– 8. Study Question: What are the mechanisms of atypical atrial flutter (AFl) arising in the right atrium? Methods: Activation and entrainment mapping were performed in 372 consecutive patients referred for catheter ablation of AFl. Atypical AFl was defined as AFl other than typical counterclockwise or clockwise AFl utilizing the cavotricuspid isthmus. Among the 372 patients, 88% were found to have typical isthmus-dependent AFl, and 4% were found to have AFl arising in the left atrium. Thirty-six episodes of atypical right AFl were found in 28 patients (8%). Six of the patients had structural heart disease, but none had an atriotomy. Results: In 24 episodes of atypical right AFl in 15 patients (54%), the mechanism was found to be lower loop reentry, a reentrant circuit in the lower portion of the right atrium that utilized the cavotricuspid isthmus. In 4 of 28 patients (14%), there was counterclockwise reentry that utilized the
Antiarrhythmic Drug Therapy in the Multicenter UnSustained Tachycardia Trial (MUSTT): Drug Testing and As-Treated Analysis Wyse DG, Talajic M, Hafley GE, et al. J Am Coll Cardiol 2001;38: 344 –51. Study Question: The results of MUSTT originally were analyzed on an intention-to-treat basis, and antiarrhythmic drug therapy was found to confer no survival advantage to patients with coronary artery disease (CAD), an ejection fraction (EF) ⱕ0.40, nonsustained ventricular tachycardia (VT) and inducible VT. This study reanalyzed the results of MUSTT using an as-treated analysis.
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cavotricuspid isthmus and short-circuited the eustachian ridge barrier. Eight episodes in 7 patients (25%) were determined to be caused by upper loop reentry, a reentrant circuit involving the upper portion of the right atrium and not utilizing the cavotricuspid isthmus. Finally, in 2 patients (7%), there was reentry around areas of scar in the posterolateral right atrium. Conclusions: Mechanisms of flutter that are dependent on the cavotricuspid isthmus are present in approximately two-thirds of patients with atypical right AFl. Non-isthmusdependent mechanisms of flutter are present in approximately one-third of patients with atypical right AFl. Perspective: The results of this study imply that a majority of atypical right AFls can be successfully ablated by the conventional technique of creating block in the cavotricuspid isthmus. The right AFls that are not isthmusdependent are more challenging to ablate, but account for only approximately 2% of patients referred for ablation of AFl. FM
have AVNRT or AVRT. However, false negative ATP tests are common. Perspective: ATP is not available in the United States, but it is likely that similar results can be achieved with adenosine at a starting dose of 6 mg, with repeated injections in 6 mg increments until one of the end points of the ATP test is reached. However, the clinical value of this type of testing is limited since a patient with rapid palpitations often may have AVNRT or AVRT despite a negative bedside test. FM
Value of Programmed Ventricular Stimulation for Prophylactic Internal Cardioverter-Defibrillator Implantation in Postinfarction Patients Preselected by Noninvasive Risk Stratifiers Schmitt C, Barthel P, Ndrepepa G, et al. J Am Coll Cardiol 2001;37:1901–7. Study Question: Can a combination of noninvasive tests and programmed ventricular stimulation (PVS) shortly after a myocardial infarction (MI) identify high-risk patients who benefit from an internal cardioverter-defibrillator (ICD)? Methods: Noninvasive evaluation of ejection fraction (EF), ventricular ectopy, heart rate variability and late potentials was performed in 1436 patients with an acute MI. Based on this assessment, 194 patients who were ⱕ75 years in age were identified as being high-risk and advised to undergo PVS. Ninety-eight of these 194 patients consented to PVS, which was performed a median of 18 days post-MI. An ICD was implanted if sustained, monomorphic ventricular tachycardia (VT) was inducible by PVS. Results: Sustained, monomorphic VT was induced in 21 of 98 patients who underwent PVS, and an ICD was implanted in 20 of these patients. During a mean follow-up of approximately 600 days, sudden death, VT or cardiac arrest occurred in 33% of patients with a positive response to PVS, compared to 2.6% with a negative response (p⬍0.001). Cardiac mortality was 4.7 times more likely in the high-risk patients who declined PVS than in those who underwent PVS. Conclusion: A combination of noninvasive testing and PVS identifies high-risk patients who benefit from prophylactic implantation of an ICD after an acute MI. Perspective: The patients in this study overlap with the patients included in prior post-infarction trials (MUSTT and MADIT) that have demonstrated the ICD to have a beneficial effect on survival, and the results therefore are not surprising. A notable difference is that a low EF plus nonsustained VT were required for entry into MUSTT and MADIT, while in the present study, simply a low EF was sufficient for a patient to undergo PVS. However, largerscale studies are needed before PVS can be recommended in post-MI patients with a low ejection fraction who do not have nonsustained VT. FM
The Adenosine Triphosphate Test: A Bedside Diagnostic Tool for Identifying the Mechanism of Supraventricular Tachycardia in Patients With Palpitations Viskin S, Fish R, Glick A, Glikson M, Eldar M, Belhassen B. J Am Coll Cardiol 2001;38:173–7. Study Question: Prior studies have demonstrated that injection of adenosine triphosphate (ATP) can uncover evidence of dual atrioventricular nodal pathways or a concealed accessory pathway. The purpose of this study was to determine how often the ATP test identifies patients with palpitations who have atrioventricular nodal reentrant tachycardia (AVNRT) or atrioventricular reentrant tachycardia (AVRT). Methods: A history of rapid palpitations of sudden onset was present in 140 patients in whom tachycardia either was undocumented or documented but of unclear mechanism. These patients underwent an ATP test followed by an electrophysiology test. ATP was administered intravenously during sinus rhythm at the bedside at an initial dose of 10 mg, with repeated injections in 10 mg increments until an end point was reached. The ATP test was positive when it revealed dual atrioventricular nodal physiology or atrioventricular reentrant echo beats. The test was negative when high-degree atrioventricular block occurred without any positive findings. Results: The ATP test was positive in 63% of patients and negative in 37%. The sensitivity of a positive ATP test for AVNRT or AVRT was 71%, with a positive predictive value of 93%. A negative ATP test had a specificity of 76%, with a negative predictive value of 37%. Conclusions: A positive ATP test is helpful in predicting which patients with palpitations of unclear mechanism
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