"It cant be PEA if the rate is over 150" -- ??

[Thunderchild145]

I've never seen SVT be the cause of cardiac arrest. SVT being the cause of significant perfusion problems? Yea. PEA? No. So, my recommendations are fluid bolus and then escalating cardioversion (up to 360). If Sync-ing at 360 doesn't fix this, then you might want to consider something else. (Like Transport)

[Ace844]

(J Appl Physiol 101: 102-110 @ 2006. First published March 24, 2006; doi:10.1152/japplphysiol.01334.2005

8750-7587/06 Ischemia induces aggravation of baseline repolarization abnormalities in left ventricular hypertrophy: a deleterious interaction

Aigars Rubulis,1 Jens Jensen,1 Gunilla Lundahl,1 Jari Tapanainen,1 and Lennart Bergfeldt1,2

1Department of Cardiology, Karolinska University Hospital Solna, Karolinska Institutet, Stockholm; and 2Department of Cardiology, Sahlgrenska University Hospital, University of Gothenburg, Gothenburg, Sweden

Submitted 19 October 2005 ; accepted in final form 6 March 2006)

Epidemiological studies show that left ventricular hypertrophy (LVH) and hypertension (HT) in coronary artery disease increases the risk for cardiovascular events including sudden cardiac death (SCD). According to experimental studies, myocardial hypertrophy is associated both with altered electrophysiological properties (including prolonged repolarization) and increased vulnerability to ischemia. However, human data to support a repolarization-related mechanism for the increased SCD risk has not been provided. We therefore studied 187 patients undergoing three-dimensional vectorcardiographic monitoring during coronary angioplasty. Eight parameters reflecting different aspects of ventricular repolarization were used: 1) the ST segment (ST-VM and STC-VM), 2) the T vector (QRS-T angle, Televation, and Tazimuth), and 3) the T vector loop (Tavplan, Teigenv, and Tarea). Data collection was performed at rest and at the time of maximum ischemia during coronary occlusion. The patients were divided into three groups: 33 patients with ECG signs of LVH (18 with HT), 54 with HT but without LVH signs, and 100 patients with neither. Coronary artery disease patients with LVH not only had the most abnormal baseline repolarization (as expected) but also a significantly more pronounced repolarization response during coronary occlusion, whereas HT patients had mean parameter values between LVH patients and those without neither HT nor LVH signs. Because there is a relation between increased SCD risk and repolarization disturbances in various clinical settings, the results of the present study are in agreement with animal data and epidemiological observations, although other factors than disturbed repolarization might be of importance.

[Ace844]

Hello Everyone,

Here's an SVT related study which i thought you may all find interesting, and it relates somewhat to this topic.

HTH,

ACE844

(The American Journal of Emergency Medicine

Volume 24 @ Issue 4 , July 2006, Pages 402-406

doi:10.1016/j.ajem.2005.12.004

Copyright © 2006 Elsevier Inc. All rights reserved.

Original Contribution

A new algorithm for the initial evaluation and management of supraventricular tachycardia

H.C. Tyler Richmond MDa, Lee Taylor III MDa, Michael H. Monroe MDa and Laszlo Littmann MD, a,

aDepartment of Internal Medicine, Carolinas Medical Center, Charlotte, NC 28232, USA

Received 9 September 2005; revised 28 November 2005; accepted 1 December 2005. Available online 17 June 2006.)

Original Contribution

A new algorithm for the initial evaluation and management of supraventricular tachycardia

H.C. Tyler Richmond MDa, Lee Taylor III MDa, Michael H. Monroe MDa and Laszlo Littmann MD, a,

aDepartment of Internal Medicine, Carolinas Medical Center, Charlotte, NC 28232, USA

Received 9 September 2005; revised 28 November 2005; accepted 1 December 2005. Available online 17 June 2006.

Abstract

Interpretations by physicians and those generated by electrocardiograph computer softwares have poor ability to recognize different types of supraventricular tachycardia (SVT). Therefore, we developed and tested a new SVT algorithm based on easily identifiable morphological characteristics and a simple dichotomous yes/no format regarding initial electrocardiographic manifestation and response pattern. The algorithm was then tested by medical house staff during the initial evaluation of 50 adult ED and cardiac intensive care unit patients suspected of having SVT. For a wide representation of SVTs, the new algorithm gave an overall diagnostic accuracy rate of 90%. Adenosine use was limited to 54% of the cases. No patient developed hemodynamic instability after algorithm-dictated interventions were carried out. Electrocardiograph computer-generated diagnoses correctly identified the specific type of SVT in 38% of the cases. This study shows the effectiveness of the proposed new algorithm in the rapid bedside evaluation and management of SVTs and confirms that computer-generated diagnoses are unreliable.

Article Outline

1. Introduction

2. Methodology

3. Results

4. Discussion

4.1. Existing SVT algorithms

4.2. Construction of the new SVT algorithm

4.3. Clinical utility of the new algorithm

5. Limitations

6. Summary

References

1. Introduction

Recognizing, diagnosing, and properly treating supraventricular tachycardia (SVT) are common tasks that emergency medicine and other physicians face. Rapid diagnosis and appropriate management can help decrease the potential morbidity and mortality associated with this class of arrhythmias. Thus, recognition and management of SVT have remained an integral component of physician education in the form of Advanced Cardiac Life Support (ACLS) [1].

Despite this training, physicians still have a poor ability to properly diagnose SVT. Two studies suggested that medical house staff and attending physicians diagnose narrow complex tachycardias incorrectly in approximately 40% of cases [2] and [3]. Overuse of adenosine is common [4] and with certain forms of SVT may actually decrease diagnostic success [2] and [4]. In addition, physicians are often misled by the frequently incorrect computer-generated interpretations of SVTs [5]. Correct SVT recognition may be problematic because the current ACLS algorithm for SVT requires a positive identification of the type of SVT at the initiation of the algorithm and omits frequently misdiagnosed SVTs such as sinus tachycardia [1].

In response to these areas of concern, we developed a new algorithm based on the following principles: (1) initial categorization of the SVT according to its electrocardiographic (ECG) manifestation rather than a specific diagnosis; (2) inclusion of all relatively frequent forms of SVT; and (3) clear distinction between SVT and wide complex tachycardia of uncertain etiology. We used a dichotomous yes/no flow sheet format dependent on the initial ECG manifestation of the tachycardia and the subsequent response pattern to maneuvers that block the AV node. The use of adenosine was only permitted under specific, well-defined circumstances. Fig. 1 shows our new SVT algorithm with detailed instructions on the appropriate use of various AV nodal blocking agents incorporated in footnotes [6] and [7].

(51K)

Fig. 1. New algorithm for the initial evaluation and management of SVT.

This pilot study was designed as a prospective investigation to determine whether our algorithm could aid medical house staff in diagnosing and treating SVTs at the bedside.

2. Methodology

During a 7-month period, a sample of 50 patients was collected from our university-associated community teaching hospital with its 114 000–visits-per-year ED and 20-bed cardiac intensive care unit. We educated emergency medicine, family practice, internal medicine, and physical medicine and rehabilitation residents on the patient entry criteria and use of the algorithm. Patients presenting with symptomatic tachycardia were entered into the study by medical house staff at their discretion. If a patient was suspected of having an SVT, an unused printed copy of the algorithm was obtained by each resident and reviewed. The initial ECGs were recorded using GE-Marquette ECG carts (Milwaukee, WI) fitted with the 12-SL interpretative software.

The diagnosis of SVT was allowed only under the following specific circumstances: (1) rate > 100/min; (2) QRS duration ≤ 0.11 second; or (3) wide complex tachycardia (QRS duration ≥ 0.12 second) with a typical bundle-branch block morphology plus constant P-QRS relationship or a preexisting bundle-branch block or an intraventricular conduction disturbance with a perfectly identical QRS morphology plus a constant P-QRS relationship [8]. All other wide complex tachycardias were excluded to follow the appropriate ACLS guidelines for wide complex tachycardia of uncertain type or ventricular tachycardia [1]. Of note, the house staff were encouraged to exclude patients with obvious sinus tachycardia of an identifiable cause and those who had a known history of atrial fibrillation (AF) and who presented with an increased ventricular rate. Once a resident determined eligibility for the study, he or she followed the algorithm with all physiological, pharmacologic, and electrical interventions performed accordingly. Rhythm strips and/or further ECGs were encouraged and obtained at the discretion of each resident.

Starting at the top, the algorithm (Fig. 1) first branches with the question of whether the rhythm is regular. For a rhythm determined to be regular, the next distinction is whether it is sinus tachycardia. Identifying characteristics of sinus tachycardia (slightly irregular rhythm; upright P waves in leads I, II, and aVF; short normal PR intervals; the presence of premature atrial complexes; and heart rate modification by autonomic maneuvers) are offered for review. If the tachycardia is determined to be sinus, the algorithm terminates with “identify and treat the cause.” A further attempt to immediately establish the mechanism of the remaining regular tachycardias is not required. Instead, instruction is given to apply physiological or pharmacologic maneuvers that are intended to result in AV nodal block. Choices to induce AV block are listed and repeated attempts to block down the AV node are encouraged. Only if AV block cannot be achieved by any means is D/C cardioversion offered. If AV block is achieved, then the next question is whether the tachycardia is terminated. If the tachycardia is terminated with AV block, then the general diagnosis of reentrant tachycardia (AV nodal reentry or AV macro-reentry) is made and the initial treatment has been accomplished. If, however, AV block does not result in termination of the tachycardia, then atrial flutter or ectopic atrial tachycardia is unmasked as the diagnosis and standard ACLS treatment options are presented for consideration.

Going back to the original branch point, if analysis of the ECG reveals an irregular rhythm, then the operator should determine if group beatings are present. If they are present, then the most likely diagnosis is a variable blocking of either atrial flutter or ectopic atrial tachycardia and standard treatment options are given for consideration. If there is no group beating present (ie, the tachycardia is irregularly irregular), then one is asked to look for discrete P waves. The presence of distinct P waves or sinus beats suggests multifocal atrial tachycardia (MAT), whereas their absence confirms a diagnosis of AF. For both types of arrhythmias, generally accepted treatment options are provided.

While following the said algorithm in evaluating and treating the patients, the house staff marked a decision-intervention line tracing their path on the printed form. On the back of the page, each resident made note of the following: (1) patient identification data; (2) clinical diagnosis; (3) tachycardia diagnosis after use of the algorithm; (4) general description of clinical course and events, including untoward effects of therapy and hemodynamic problems; (5) general comments, problems, or recommendations for the algorithm; and (6) patient disposition. We reviewed the data forms biweekly to ensure that the entries met the appropriate requirements. After 50 samples were collected, an electrophysiologist reviewed all ECGs and rhythm strips. His interpretations were used as the correct diagnoses.

3. Results

A total of 24 medical house staff participated in the study. There were 25 cases entered in the cardiac intensive care unit, 23 in the ED, and 2 in hospital wards. In Table 1, the tachycardia diagnoses as determined by the house staff's use of the algorithm are compared with the electrophysiologist's interpretation of the ECGs and rhythm strips. A wide variety of SVTs were encountered, and, appropriately, no case of ventricular tachycardia was entered. The medical house staff diagnoses were correct in 45 of the 50 cases (90%; see Table 1). Adenosine was used on 27 occasions (54%). There was no instance of hemodynamic instability after the algorithm-dictated interventions were carried out, and resident comments on the algorithm were uniformly positive.

Table 1.

Supraventricular tachycardia diagnoses SVT diagnoses by house staff Total no. of diagnoses No. of correct diagnoses No. of incorrect diagnoses Correct diagnoses

Sinus tachycardia 6 6 0

Reentrant SVT 20 19 1 Ectopic atrial tachycardia

AF 13 11 2 Multifocal tachycardia for both cases

Atrial flutter 7 5 2 AF for both cases

MAT 3 3 0

Ectopic atrial tachycardia 1 1 0

Total 50 45 5

The ECG computer-generated diagnoses were correct in only 24 of the 50 cases (48%); of these, a specific diagnosis (ie, other than SVT) was given in only 19 (38%). In 2 cases, an undetermined rhythm was noted; in 1 case, a wide QRS tachycardia was reported. The computer interpretation was incorrect on 23 occasions (46%). Through the implementation of the algorithm, the house staff rejected all 23 incorrect diagnoses generated by the ECG computer. Of these, another incorrect diagnosis was reached on 2 occasions, whereas the correct diagnosis was reached on 21 occasions.

4. Discussion

Our proposed and tested SVT algorithm provides an organized, stepwise process in the interpretation of SVTs and will likely improve medical decision making and patient management.

4.1. Existing SVT algorithms

To our knowledge, this is the first prospective evaluation of the clinical utility of an SVT algorithm in the literature. Despite the enormous scale on which the current ACLS guidelines are being taught, we are not aware of any attempt to verify its efficacy or usefulness. Other SVT algorithms have been published, but they appear too cumbersome for general use and subsequently have not been tested for their didactic or clinical value [6], [9] and [10].

4.2. Construction of the new SVT algorithm

The new SVT algorithm was constructed to follow easily recognizable morphological characteristics and a physiologically based logical path. It first separates regular and irregular SVTs—a generally easy task but one that is sometimes aided by the use of calipers. Of the regular SVTs, sinus tachycardia is the most common. Positive identification of this rhythm through reminders of its typical manifestations is a required step to avoid the use of adenosine and to emphasize the fact that sinus tachycardia is rarely a primary arrhythmia. Residents were instructed to always consider atrial flutter with 2:1 block, especially in patients who have a regular tachycardia with rates between 130 and 160 beats/min. A second, hidden P wave can sometimes be found by halving of the apparent P-P interval.

Maneuvers are then offered to block down the AV node. Many strategies to block the node are listed with encouragement to try other strategies if one proves unsuccessful. Instructions are given on the appropriate use of the various AV nodal blocking agents. If AV block results in tachycardia termination, then AV nodal conduction must be an integral part of the tachycardia circuit defining AV nodal or AV macro-reentrant tachycardia as the etiology. If AV nodal block did not result in tachycardia termination, then the site of the regular SVT must have been above the node; ie, atrial flutter or ectopic atrial tachycardia with constant blocking ratio was the diagnosis.

Of the irregular tachycardias, the first distinction is between regular rhythms that appear irregular because of variable AV block and truly irregular ones. Group beatings are defined as episodes of regular SVT separated by pauses that almost always represent atrial tachycardia or atrial flutter with variable block. The irregularly irregular SVTs are most often AF. Multifocal atrial tachycardia, however, may also manifest as an irregularly irregular SVT and is frequently incorrectly diagnosed as AF both by computer interpretation software and by physicians. A search for distinct sinus beats is required to avoid this misdiagnosis and should prompt the physician to consider the diagnosis of MAT if found.

In our SVT algorithm, some therapy occurs simultaneously with interpretation, but, overall, we did not focus on details of the acute treatment of various types of SVT. The reentrant paroxysmal SVTs were terminated as part of the evaluation process. A common treatment box was offered for atrial tachycardia/atrial flutter with constant blocking ratio (regular SVT), for atrial tachycardia/atrial flutter with variable blocking ratio (irregular SVT with group beating), and for AF (irregularly irregular SVT without distinct sinus beats). This treatment box included consideration of anticoagulation, rate control, and antiarrhythmic management, without specifying the various antiarrhythmic treatment choices. With both sinus tachycardia and MAT, physicians were encouraged to identify and treat the underlying cause of these typically secondary tachyarrhythmias.

4.3. Clinical utility of the new algorithm

This pilot study, although not statistically evaluated, suggests that our proposed algorithm is effective in the rapid bedside diagnosis and management of SVT. It disallows consideration of wide complex tachycardia of uncertain etiology from the outset through a more rigorous definition of SVT. It requires no a priori diagnosis, only the ability to answer yes/no questions based on standard ECG observations. Imperative for any guideline, it follows a logical pattern that is conducive for quick comprehension and recall. Furthermore, the use of adenosine is potentially decreased by separating out rhythms (namely, sinus tachycardia, MAT, and AF) whose diagnosis could be hampered by its use [2] and [4].

For patients presenting with new-onset symptomatic SVT, the bedside diagnostic accuracy rate was 90% when used by a representative group of house staff. A wide variety of supraventricular tachyarrhythmias were entered and, of note, no primary ventricular rhythm was included. It is not known, however, how many attempts at inclusion were aborted secondary to a failure to meet the strict SVT definition. Sinus tachycardia was correctly diagnosed without the use of adenosine in all 6 cases, and 19 of 20 reentrant tachycardias were correctly identified and terminated with the appropriate use of AV nodal blocking maneuvers (mostly adenosine). Overall, the use of adenosine was not necessary to elucidate the correct diagnosis or to initiate treatment in almost half of the cases.

Of the 5 incorrect diagnoses made by the house staff, 2 occurred secondary to the occasional difficulty in distinguishing between the presence of P waves and that of AF waves in irregular rhythms without group beatings. Two other incorrect diagnoses were the result of misreading the presence or absence of group beatings in rapid irregular rhythms. The last incorrect diagnosis occurred through inappropriate use of the algorithm where a clearly irregular rhythm with group beatings was considered to be a regular rhythm. None of these said patterns of mistakes warrants a change in the algorithm as one cannot account for all reader abilities in such a format.

5. Limitations

Weaknesses of the study include the lack of electrophysiological study to verify final diagnoses, the small sample size, user discretion on entry, and the lack of a controlled design. It is also not known how the algorithm would have worked with attending physicians. Based on well-described ECG principles, we feel that electrophysiological study is not necessary to make the general diagnostic distinctions called for by the algorithm [6], [9], [10], [11] and [12]. The user discretion was to avoid an abundance of obvious rhythms (trivial sinus tachycardia, AF) that would falsely inflate the overall accuracy rate. Unfortunately, an effective controlled trial is difficult to design and to implement as teaching of the algorithm may induce bias. A future controlled design could best be approached with a follow-up sequential study where house staff would collect electrocardiograms demonstrating SVT based on their use of the current ACLS SVT guidelines, followed by the teaching and use of our proposed new algorithm to collect cases. Relative usefulness could then be determined by comparing the 2 accuracy rates.

6. Summary

The proposed new algorithm appears to be effective in the rapid bedside evaluation and management of SVTs and may prove valuable in the setting of an ED.

References

[1] The American Heart Association in collaboration with the International Liaison Committee on Resuscitation (ILCOR), Guidelines 2000 for cardiopulmonary resuscitation and emergency cardiovascular care: an international consensus on science, Circulation 102 (2000) (Suppl), pp. I1–I384.

[2] J.B. Conti, L. Belardinelli and A.B. Curtis, Usefulness of adenosine in diagnosis of tachyarrhythmias, Am J Cardiol 75 (1995), pp. 952–955. Abstract | PDF (572 K)

[3] D.J. O'Rourke, R.T. Palac and J.T. Schindler et al., Clinical utility of adenosine in difficult to diagnose tachyarrhythmias, Clin Cardiol 22 (1999), pp. 633–639.

[4] B.P. Knight, A. Zivin and J. Souza et al., Use of adenosine in patients hospitalized in a university medical center, Am J Med 105 (1998), pp. 275–280. SummaryPlus | Full Text + Links | PDF (118 K)

[5] F. Bogun, D. Anh and G. Kalahasty et al., Misdiagnosis of atrial fibrillation and its clinical consequences, Am J Med 117 (2004), pp. 636–642. SummaryPlus | Full Text + Links | PDF (781 K)

[6] C. Blomström-Lundquist, M.M. Scheinman and E.M. Aliot et al., ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias—executive summary: a report of the American College of Cardiology, American Heart Association Task Force on Practice Guidelines, and the European Society of Cardiology Committee for Practice Guidelines, J Am Coll Cardiol 42 (2003), pp. 1493–1531.

[7] L. Littmann, J.D. Anderson and M.H. Monroe, Adenosine and Aggrenox: a hazardous combination, Ann Intern Med 137 (2002), pp. e–76.

[8] L. Littmann and M.M. McCall, Ventricular tachycardia may masquerade as supraventricular tachycardia in patients with pre-existing bundle branch block: a potential cause of misdiagnosis and inappropriate management, Ann Emerg Med 26 (1995), pp. 98–101. SummaryPlus | Full Text + Links | PDF (329 K)

[9] F.W. Bär, P. Brugada and W.R.M. Dassen et al., Differential diagnosis of tachycardia with narrow QRS complex (shorter than 0.12 second), Am J Cardiol 54 (1984), pp. 555–560. Abstract

[10] G.K. Jones, A practical approach to narrow complex tachycardia, Int Med (1996), pp. 81–94.

[11] L. Littmann, J. Tenczer and T. Fenyvesi, Atrioventricular nodal reentrant paroxysmal supraventricular tachycardia, Arch Intern Med 144 (1984), pp. 129–131. Abstract-MEDLINE | Abstract-EMBASE

[12] L.I. Ganz and P.L. Friedman, Supraventricular tachycardia, N Engl J Med 332 (1995), pp. 162–173. Abstract-EMBASE | Abstract-MEDLINE | Full Text via CrossRef