History

Fact Explanation
Paroxysmal nature of symptoms Interference dissociation is a term used to denote Atrio-Ventricular AV) dissociation due to interference. It may be bidirectional or unidirectional with primary block in the opposite direction. Interference dissociation between a sino-atrial and an A-V nodal rhythm is the most common form.But it can occur between 2 pacemakers in any part of the heart and even possible to have interference between 2 foci in a single heart chamber, without involving the A-V junction. In almost all instances, the lower focus beats faster than the upper focus and a retrograde block is a must to protect the upper focus. There are several ways in which interference dissociation may originate and could be divided into 3 categories. Escape mechanism in which lower focus beat slower than the upper, Homogenetic mechanism in which lower focus is slightly faster than the upper and heterogenetic mechanism in which lower focus beats much faster than the upper focus. [1]
Asymptomatic [1] [2] [3] Only around 0.04% in the general population could be symptomatic and usually present to primary care with features of atypical chest pain, exertional dyspnea, and the routing ECG detect the features of interference dissociation [1] [6]
Exertional dyspnea/ Chest pain [1] [2] [3] As there's a shift between the normal sinus rhythm and interference dissociation, and resultant arrhythmia, patient can suffer from symptoms of angina such as exertional chest pain or dyspnoea due to ischemia of the heart [1] [2] [4] [5]
Light-headedness/ Syncope [1] [2] [3] Due to inadequate cerebral circulation owing to a rapid heart rate or tachyarrhythmia depressing the sinus pacing, causing a period of asystole which is produced at the end of the tachycardic episode. [2] [3] [4] [5]
Palpitations [1] [2] [3] These can be felt as pauses or nonconducted beats followed by a sensation of a strong heartbeat, or they are described as irregularities in heart rhythm [2] [3] [4] [5]
Fatigue, malaise [1] [2] [3] Due to inadequate cerebral circulation owing to a rapid heart rate or tachyarrhythmia depressing the sinus pacing, causing a period of asystole which is produced at the end of the tachycardic episode. [2] [3]
References
  1. MILLER R., SHARRETT R. H.. Interference Dissociation. Circulation [online] 1957 November, 16(5):803-829 [viewed 12 July 2014] Available from: doi:10.1161/01.CIR.16.5.803
  2. BLOMSTRöM-LUNDQVIST CARINA, et al. ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias —executive summary. Journal of the American College of Cardiology [online] 2003 October, 42(8):1493-1531 [viewed 12 July 2014] Available from: doi:10.1016/j.jacc.2003.08.013
  3. ALZAND B. S. N., CRIJNS H. J. G. M.. Diagnostic criteria of broad QRS complex tachycardia: decades of evolution. Europace [online] December, 13(4):465-472 [viewed 12 July 2014] Available from: doi:10.1093/europace/euq430
  4. SANGHVI LM, MISRA SN. ELECTROCARDIOGRAMS WITH SHORT P-R INTERVAL AND ABERRANT QRS COMPLEX Br Heart J [online] 1958 Jul, 20(3):357-362 [viewed 12 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC479678
  5. HOFFMAN I, MORRIS MH, FRIEDFELD L, GITTLER RD. ABERRANT BEATS OF WOLFF-SCHAMROTH L. Principles governing 2:1 AV block with interference dissociation. Br Heart J [online] 1969 Nov, 31(6):780-786 [viewed 12 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC487591
  6. SINGH GAGAN D., WONG GARRET B., SOUTHARD JEFFREY A., AMSTERDAM EZRA A.. Food for Thought: Atrioventricular Dissociation. The American Journal of Medicine [online] 2013 December, 126(12):1050-1053 [viewed 13 July 2014] Available from: doi:10.1016/j.amjmed.2013.09.001

Examination

Fact Explanation
Tachycardia/Bradycardia [3] [4] [5] [6] Pulse rate could be either fast or slow depending on the arrhythmia [3] [4] [5] [6]
Irregularity in pulse [3] [4] [5] [6] Pulse rhythm is usually irregularly irregular due to difference in the atrial and ventricular rhythms. In the presence of a irregularly irregular pulse, pulse deficit should be calculated in which one examiner auscultates the heart and get the heart rate and the other examiner gets the pulse rate by palpating the radial pulse. Pulse deficit is the difference between these 2 values. [3] [4] [5] [6]
Hypotension [3] [4] [5] [6] Blood pressure could be low in ventricular tachycardia [3] [4] [5] [6]
Intermittent Cannon Wave in Jugular venous pulse [1] Intermittent cannon a waves can occur when atria and ventricles contract simultaneously [2]
Variable intensity of the first heart sound [2] This occurs due to atrioventricular dyssynchrony [2]
References
  1. CHEN D., PAI P.-Y.. Cannon A Wave. Circulation [online] 2009 April, 119(13):e381-e383 [viewed 12 July 2014] Available from: doi:10.1161/CIRCULATIONAHA.108.833095
  2. FELNER JM, WALKER HK, HALL WD, HURST JW. The First Heart Sound [online] 1990 [viewed 12 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/21250175
  3. SCHAMROTH L, DUBB A. Escape-capture bigeminy. Mechanisms in S-A block, A-V block, and reversed reciprocal rhythm. Br Heart J [online] 1965 Sep, 27(5):667-669 [viewed 12 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC469759
  4. SANGHVI LM, MISRA SN. ELECTROCARDIOGRAMS WITH SHORT P-R INTERVAL AND ABERRANT QRS COMPLEX Br Heart J [online] 1958 Jul, 20(3):357-362 [viewed 12 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC479678
  5. MILLER R., SHARRETT R. H.. Interference Dissociation. Circulation [online] 1957 November, 16(5):803-829 [viewed 12 July 2014] Available from: doi:10.1161/01.CIR.16.5.803
  6. BLOMSTRöM-LUNDQVIST CARINA, et al. ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias —executive summary. Journal of the American College of Cardiology [online] 2003 October, 42(8):1493-1531 [viewed 12 July 2014] Available from: doi:10.1016/j.jacc.2003.08.013

Differential Diagnoses

Fact Explanation
First degree heart block [1] [2] This has a long P-R interval, with the P wave lying close to the preceding QRS complex. But in a long tracing when the heart rate changes either spontaneously or in response to the sinus reactions the P-R interval will remain constant. [1]
Second degree heart block with 2:1 block or Wenckebach phenomenon [1] [3] In 2:1 block, the relationship will become clear when the rate of the sinus rhythm changes. But in the Wenckebach phenomenon the ventricular rhythm is so irregular, that it can be differentiated. [1]
Almost complete heart block with V-A or A-V response [1] Complete or almost complete antegrade block and normal retrograde conduction may lead to interference dissociation or vise versa. [1]
Complete A-V block [1] [4] The rate of atria or ventricles is not an absolute criterion but the main thing of differentiation is that in complete block in long tracings there will never be evidence of conduction across the A-V junction.[1]
Atrial fibrillation with complete block [1] [5] this presents same as atrial fibrillation with interference dissociation. But, when the dissociation is of short duration, it is probably due to interference. [1]
Interference dissociation between an S-A and A-V nodal rhythm with aberrant ventricular conduction [1] [6] Idioventricular rhythm can be differentiated from an S-A and A-V nodal rhythm in the presence of bundle branch block. Long tracings show the onset and termination of interference dissociation, or the presence of isolated extra systoles or escaped beats and ventricular captures or fusion beats are diagnostic of an idioventricular rhythm. [1] [6]
Ventricular parasystole [1] [7] In parasystole the rhythm of the lower center is slower than the upper. The ventricular center is protected from the higher center by an entrance block, that is, there is unidirectional forward block into the para systolic center and retrograde interference. This is the reverse of ordinary interference, in which there is forward interference and retrograde block. [1]
References
  1. MILLER R., SHARRETT R. H.. Interference Dissociation. Circulation [online] 1957 November, 16(5):803-829 [viewed 12 July 2014] Available from: doi:10.1161/01.CIR.16.5.803
  2. CRISEL R. K., FARZANEH-FAR R., NA B., WHOOLEY M. A.. First-degree atrioventricular block is associated with heart failure and death in persons with stable coronary artery disease: data from the Heart and Soul Study. European Heart Journal [online] December, 32(15):1875-1880 [viewed 12 July 2014] Available from: doi:10.1093/eurheartj/ehr139
  3. LEE Y.-S., KIM S. Y., KIM K. S., KIM Y. N.. Intra-His bundle block in second-degree Mobitz I atrioventricular block with right bundle branch block. Europace [online] December, 11(9):1251-1252 [viewed 12 July 2014] Available from: doi:10.1093/europace/eup153
  4. MOYSSAKIS IOANNIS, LIONAKIS NIKOLAOS, VLAHODIMITRIS IOANNIS, VOTTEAS VASSILIOS. Complete heart block and severe aortic stenosis in a patient with rheumatoid arthtritis: a case report. Array [online] 2009 December [viewed 12 July 2014] Available from: doi:10.1186/1757-1626-2-126
  5. BAJPAI A., ROWLAND E.. Atrial fibrillation. Continuing Education in Anaesthesia, Critical Care & Pain [online] 2006 December, 6(6):219-224 [viewed 12 July 2014] Available from: doi:10.1093/bjaceaccp/mkl051
  6. GRESSIN VIRGINIE, LOUVARD YVES, PEZZANO MICHEL, LARDOUX HARVé. Significance of accelerated idioventricular rhythms during thrombolysis for acute myocardial infarction. Journal of the American College of Cardiology [online] 1991 February [viewed 12 July 2014] Available from: doi:10.1016/0735-1097(91)91032-A
  7. MURAKAWA Y., INOUE H., KOIDE T., NOZAKI A., SUGIMOTO T.. Reappraisal of the coupling interval of ventricular extrasystoles as an index of ectopic mechanisms. Heart [online] 1992 December, 68(12):589-595 [viewed 12 July 2014] Available from: doi:10.1136/hrt.68.12.589

Investigations - for Diagnosis

Fact Explanation
Electrocardiogram [1] [2] [4] Findings will show the underlying rhythm and P-wave morphology. P waves and QRS complexes of ECG will have no fixed temporal relationship to each other in complete AV dissociation,. It also helps to exclude other differentials. [1]
serum Digoxin level [3] Digoxin toxicity can cause various conduction abnormalities, therefore to exclude toxicity, serum Digoxin level is done [3]
Exercise ECG [5] sometimes, the arrhythmias are apparent only when the heart is exerted, therefore, this is done when the diagnosis is not apparent on resting ECG.
Echocardiography [6] Atrioventricular dissociation can be easily detected using different echocardiographic modalities like M-mode, mitral valve movement, flow Doppler, or tissue Doppler [6]
References
  1. MILLER R., SHARRETT R. H.. Interference Dissociation. Circulation [online] 1957 November, 16(5):803-829 [viewed 12 July 2014] Available from: doi:10.1161/01.CIR.16.5.803
  2. SANGHVI LM, MISRA SN. ELECTROCARDIOGRAMS WITH SHORT P-R INTERVAL AND ABERRANT QRS COMPLEX Br Heart J [online] 1958 Jul, 20(3):357-362 [viewed 12 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC479678
  3. DODEK A. Serum digoxin test in perspective. Can Med Assoc J [online] 1977 Nov 5, 117(9):994-996 [viewed 12 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1880205
  4. SCHAMROTH L, DUBB A. Escape-capture bigeminy. Mechanisms in S-A block, A-V block, and reversed reciprocal rhythm. Br Heart J [online] 1965 Sep, 27(5):667-669 [viewed 12 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC469759
  5. BAGGISH A. L., WOOD M. J.. Athlete's Heart and Cardiovascular Care of the Athlete: Scientific and Clinical Update. Circulation [online] December, 123(23):2723-2735 [viewed 12 July 2014] Available from: doi:10.1161/​CIRCULATIONAHA.110.981571
  6. ALZAND B. S. N., CRIJNS H. J. G. M.. Diagnostic criteria of broad QRS complex tachycardia: decades of evolution. Europace [online] December, 13(4):465-472 [viewed 12 July 2014] Available from: doi:10.1093/europace/euq430

Investigations - Fitness for Management

Fact Explanation
Venography [1] Obstruction of the access vein is a well-known complication of both permanent pacemaker and implantable cardioverter defibrillation implantation, therefore this could be done prior to implantation. [1]
Renal function tests including estimated glomerular filteration rate, serum creatinine, blood urea nitrogen [2] [3] To assess renal function prior anesthesia [2]
Full blood count [3] To exclude anemia. [3]
Coagulation studies [3] To exclude any coagulopathy. [3]
References
  1. HAGHJOO M., NIKOO M. H., FAZELIFAR A. F., ALIZADEH A., EMKANJOO Z., SADR-AMELI M. A.. Predictors of venous obstruction following pacemaker or implantable cardioverter-defibrillator implantation: a contrast venographic study on 100 patients admitted for generator change, lead revision, or device upgrade. Europace [online] 2007 March, 9(5):328-332 [viewed 12 July 2014] Available from: doi:10.1093/europace/eum019
  2. SCHEFER T., WOLBER T., BINGGELI C., HOLZMEISTER J., BRUNCKHORST C., DURU F.. Long-term predictors of mortality in ICD patients with non-ischaemic cardiac disease: impact of renal function. Europace [online] 2008 August, 10(9):1052-1059 [viewed 12 July 2014] Available from: doi:10.1093/europace/eun186
  3. CORNELISSEN H.. Preoperative assessment for cardiac surgery. Continuing Education in Anaesthesia, Critical Care & Pain [online] 2006 June, 6(3):109-113 [viewed 12 July 2014] Available from: doi:10.1093/bjaceaccp/mkl013

Investigations - Followup

Fact Explanation
Electrocardiography (ECG) [1] To assess for development of any other life threatening arrhythmias such as complete heart block, and to see the arrhythmias induced by drug therapy. [1]
Echocardiography [2] To assess for ejection fraction, for the possibility of congestive cardiac failure as consequence later [2]
References
  1. MILLER R., SHARRETT R. H.. Interference Dissociation. Circulation [online] 1957 November, 16(5):803-829 [viewed 12 July 2014] Available from: doi:10.1161/01.CIR.16.5.803
  2. ALZAND B. S. N., CRIJNS H. J. G. M.. Diagnostic criteria of broad QRS complex tachycardia: decades of evolution. Europace [online] December, 13(4):465-472 [viewed 12 July 2014] Available from: doi:10.1093/europace/euq430

Management - General Measures

Fact Explanation
Acute management of in an unstable patient. [1] [2] [3] Unstable patients may present with ventricular tachycardia, therefore should be immediately cardioverted with synchronized direct current (DC cardioversion) This is done usually at a 100 J of starting energy dose. Unstable polymorphic VT is treated with immediate defibrillation. Intravenous drug therapy too can be used with Amiodarone, procainamide, sotalol or Lidocaine [1]
Acute management with Pharamacological therapy [4] Anticholinergic agents Competitive inhibitor at autonomic, postganglionic, and cholinergic receptors such as Atropine,Sulfate Increases heart rate causing increase in cardiac output. [4]
Dietary management [6] No special diets required. low-cholesterol diets, low-salt diets both recommended if in heart failure. [6]
Activity [5] [6] Increased sympathetic tone during strenuous physical exertion can precipitate many arrhythmias, Therefore it's better avoided [6]
Patient education [6] patient education regarding nature, course, prognosis of disease, the precautions after starting anti arrhythmic therapy, and precautions to be taken after pace maker implantation is needed. [6]
Patient identification [6] When a patient presents with syncope, cardiac arrest, patient identification with a bracelet/ diagnosis card is helpful for further management [6]
References
  1. HANASH CR, CROSSON JE. Emergency diagnosis and management of pediatric arrhythmias J Emerg Trauma Shock [online] 2010, 3(3):251-260 [viewed 12 July 2014] Available from: doi:10.4103/0974-2700.66525
  2. Part 7.3: Management of Symptomatic Bradycardia and Tachycardia. Circulation [online] 2005 November, 112(24_suppl):IV-67-IV-77 [viewed 12 July 2014] Available from: doi:10.1161/CIRCULATIONAHA.105.166558
  3. TRAPPE HJ. Concept of the five 'A's for treating emergency arrhythmias J Emerg Trauma Shock [online] 2010, 3(2):129-136 [viewed 12 July 2014] Available from: doi:10.4103/0974-2700.62111
  4. LEVY M. N., EDFLSTEIN J.. The Mechanism of Synchronization in Isorhythmic A-V Dissociation: II. Clinical Studies. Circulation [online] 1970 October, 42(4):689-699 [viewed 12 July 2014] Available from: doi:10.1161/01.CIR.42.4.689
  5. BUTLER JAVED. Primary Prevention of Heart Failure. ISRN Cardiology [online] 2012 December, 2012:1-15 [viewed 12 July 2014] Available from: doi:10.5402/2012/982417
  6. WOOD M. A.. Cardiac Pacemakers From the Patient's Perspective. [online] 2002 May, 105(18):2136-2138 [viewed 12 July 2014] Available from: doi:10.1161/​01.CIR.0000016183.07898.90

Management - Specific Treatments

Fact Explanation
Pharamacological therapy [1] Anticholinergic agents Competitive inhibitor at autonomic, postganglionic, and cholinergic receptors such as Atropine Sulfate Increases heart rate, causing increase in cardiac output. [1]
Pacemaker implantation [2] [3] Permanent pacing with pacemaker implantation may be necessary if there's in adequate response to drugs [2]
References
  1. LEVY M. N., EDFLSTEIN J.. The Mechanism of Synchronization in Isorhythmic A-V Dissociation: II. Clinical Studies. Circulation [online] 1970 October, 42(4):689-699 [viewed 12 July 2014] Available from: doi:10.1161/01.CIR.42.4.689
  2. ALLEN P, ROBERTSON R, TRAPP WG. Indications for Treatment of Complete Atrioventricular Dissociation Can Med Assoc J [online] 1964 Sep 5, 91(10):547-552 [viewed 12 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1927936
  3. WOOD M. A.. Cardiac Pacemakers From the Patient's Perspective. [online] 2002 May, 105(18):2136-2138 [viewed 12 July 2014] Available from: doi:10.1161/​01.CIR.0000016183.07898.90