History

Fact Explanation
Exertional dyspnea Breathlessness on mild exertion or at rest is a symptom shown to be associated with AV dissociation. It results from reduced cardiac output causing reduced tissue perfusion, particularly during irregular or a rapid heart rate.[1]
Feeling light-headed/dizziness Results from reduced cerebral perfusion at times of arrhythmias that cause reduction in cardiac output. [1]
Palpitations Changes in heart rate may be perceived by the patient as palpitations or sensation of a rapid irregular heartbeat. [1][4]
Fatigue Is a feeling of tiredness that results from reduced cardiac output associated with AV dissociation. [1]
Syncope Conditions that give rise to arrhythmias, including AV dissociation predispose a patient to cardiac syncope. There is sudden, transient loss of consciousness, which results after the brain has been deprived of oxygen for a few seconds due to the reduced cardiac output and reduced cerebral perfusion. [1][2][3]
History of Digoxin use Digoxin is a cardiac glycoside used to treat heart failure and various supraventricular tachyarrhythmias. It has a narrow therapeutic index. Therefore has a higher risk for intoxication. Digoxin intoxication can give rise to various cardiac arrhythmias including AV dissociation. [5]
References
  1. 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 01 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1927936
  2. ROLAND G. HISS, LAWRENCE E. LAMB. Electrocardiographic Findings in 122,043 Individuals.Circulation[online] 1962;25:947-961[viewed on 1 June 2014] Available from; http://circ.ahajournals.org/content/25/6/947
  3. ROBERT L. GAUER. Evaluation of Syncope. Am Fam Physician[online]2011 Sep 15;84(6):640-650[viewed on 1 July 2014 ] Available from; http://www.aafp.org/afp/2011/0915/p640.html#sec-1
  4. ALLAN V. ABBOTT. Diagnostic Approach to Palpitations. Am Fam Physician[online] 2005 Feb 15;71(4):743-750[viewed on 1 July 2014] Available from; http://www.aafp.org/afp/2005/0215/p743.html
  5. CHUNG EK. Digitalis intoxication. Postgrad Med J [online] 1972 Mar, 48(557):163-179 [viewed 01 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2495199

Examination

Fact Explanation
Variable pulse rate and volume The rate and volume of the pulse varies as a result of the changing relationship between atrial and ventricular contractions.[1][2][5]
Variable blood pressure Blood pressure is the manifestation of cardiac output and systemic peripheral resistance. Cardiac output is a manifestation of stroke volume and pulse rate. Stroke volume is affected by the pulse rate. e.g. during tachycardia the diastole shortens and ventricular filling is affected, so that the end diastolic volume reduces. This leads to a low stroke volume. In patients with AV dissociation pulse rate varies depending on the underlying cause and the blood pressure may vary depending on variations in the pulse rate. [5]
Canon 'a' waves in Jugular venous pulse When there is AV dissociation and the atria and ventricles contract at different rates, the atria may contract against closed tricuspid and mitral valves. This gives rise to canon 'a' wave, which may be felt as a 'pounding' in the neck. [4][7]
Changes in first heart sound Intensity of first heart sound may vary according to ventricular rate comparative to atrial rate. The first heart sound will be heard loud intermittently in interference-dissociation when the ventricles happen to contract shortly after the atria. [3]
Changes in systolic murmurs Beat to beat changes can be noticed in systolic murmurs. [6]
References
  1. FLETCHER E, STEVENSON M. DISSOCIATION WITH INTERFERENCE, RECIPROCAL RHYTHM, AND CORONARY SINUS RHYTHM Br Heart J [online] 1955 Jul, 17(3):285-295 [viewed 01 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC479557
  2. ORETO G, SMEETS JL, RODRIGUEZ LM, TIMMERMANS C, WELLENS HJ. Wide complex tachycardia with atrioventricular dissociation and QRS morphology identical to that of sinus rhythm: a manifestation of bundle branch reentry. Heart [online] 1996 Dec, 76(6):541-547 [viewed 02 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC484610
  3. Felner JM. The First Heart Sound. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990. Chapter 22. Available from: http://www.ncbi.nlm.nih.gov/books/NBK333/
  4. Applefeld MM. The Jugular Venous Pressure and Pulse Contour. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990. Chapter 19. Available from: http://www.ncbi.nlm.nih.gov/books/NBK300/
  5. Moran JF. Pulse. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990. Chapter 17. Available from: http://www.ncbi.nlm.nih.gov/books/NBK278/
  6. Alpert MA. Systolic Murmurs. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990. Chapter 26. Available from: http://www.ncbi.nlm.nih.gov/books/NBK345/
  7. PETER ZIMETBAUM, MARKE. J.OSEPHSON. EVALUATION OF PATIENTS WITH PALPITATIONS. New England Journal of Medicine[online] [viewed on 2 June 2014] Available from: https://uthsc.edu/cardiology/articles/Palpitations_NEJM98.pdf

Differential Diagnoses

Fact Explanation
Atrioventricular block Can present with symptoms similar to AV dissociation. [1][2]
References
  1. GABRIEL GREGORATOS. Indications and Recommendations for Pacemaker Therapy. Am Fam Physician[online]2005 Apr 15;71(8):1563-1570[viewed on 1 July 2014]Available from; http://www.aafp.org/afp/2005/0415/p1563.html
  2. ROLAND G. HISS, LAWRENCE E. LAMB. Electrocardiographic Findings in 122,043 Individuals.Circulation[online] 1962;25:947-961[viewed on 1 June 2014] Available from; http://circ.ahajournals.org/content/25/6/947

Investigations - for Diagnosis

Fact Explanation
Electrocardiogram (ECG) In complete AV dissociation, P waves do not show any fixed temporal relationship with QRS complexes. P-wave morphology depends on atrial activation. The ventricular rate may be same or faster than that of the atria. When the atrial rate and ventricular rate are the same but the P wave is not conducting,it is called an isorhythmic AV dissociation or complete AV dissociation. The rates being similar but occasionally the P wave is conducted it is known as an interference AV dissociation or incomplete AV dissociation. The ventricular rate will be faster than the atrial rate when junctional or ventricular pacemaker increases its rate of firing above that of the sinus node. Now this subsidiary pacemaker takes over the control of the ventricles while the sinus node still controls the atria, resulting in AV dissociation. When there is a block or an interference to the conduction of atrial impulses to the ventricles, atria and ventricles contract independently and the atrial rate will be faster than the ventricular rate. [1][2][3][4]
References
  1. LEVY MN, EDFLSTEIN J. The Mechanism of Synchronization in Isorhythmic A-V Dissociation: II. Clinical Studies. Circulation[online] American Heart Association. 1970;42:689-699[viewed on 30 June 2014] Available from; http://circ.ahajournals.org/content/42/4/689
  2. SLOCUM J,BYROM E,MCCARTHY L,SAHAKIAN A, SWIRYN S. Computer detection of atrioventricular dissociation from surface electrocardiograms during wide QRS complex tachycardias. Circulation [online]American Heart Association 1985;72:1028-1036[viewed on 1 July 2014] Available from; http://circ.ahajournals.org/content/72/5/1028.full.pdf+html
  3. FLETCHER E, MORTON P, MURTAGH JG, BEKHEIT S. Atrioventricular dissociation with accrochage. Br Heart J [online] 1971 Jul, 33(4):572-577 [viewed 01 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC487216
  4. FLETCHER E, STEVENSON M. DISSOCIATION WITH INTERFERENCE, RECIPROCAL RHYTHM, AND CORONARY SINUS RHYTHM Br Heart J [online] 1955 Jul, 17(3):285-295 [viewed 01 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC479557

Management - Specific Treatments

Fact Explanation
Anticholinergic medication Blocks the parasympathetic activity on the heart and increases the heart rate and cardiac output. [1]
Adrenergic agonist Medication Act by increasing heart rate and contractility . Can abolish some forms of atrial and ventricular extrasystoles. Also improve coronary artery blood flow. [4]
Antidote treatment in digitalis toxicity Digoxin immune Fab (Digibind) is an immunoglobulin fragment with a high and specific affinity for digoxin and digitoxin molecules. It acts to remove digoxin or digitoxin molecules from tissue binding sites.It is used to treat digitalis intoxication which can cause similar arrhythmia. [2][5]
Pacemaker Insertion of a permanent pacemaker is rarely needed for patients with AV dissociation. Useful for patients with bradycardia. [1][3]
Cardioversion Can be considered in hemodynamically unstable patients, for rapid restoration of sinus rhythm. [6]
References
  1. 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 01 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1927936
  2. JUNEJA D, SINGH O, BHASIN A, GUPTA M, SAXENA S, CHATURVEDI A. Severe suicidal digoxin toxicity managed with resin hemoperfusion: A case report Indian J Crit Care Med [online] 2012, 16(4):231-233 [viewed 01 July 2014] Available from: doi:10.4103/0972-5229.106511
  3. VARDAS PE, SIMANTIRAKIS EN, KANOUPAKIS EM. New developments in cardiac pacemakers. Circulation [online] 2013 Jun 11, 127(23):2343-50 [viewed 01 July 2014] Available from: doi:10.1161/CIRCULATIONAHA.112.000086
  4. STOCK JP, DALE N. Beta-adrenergic Receptor Blockade in Cardiac Arrhythmias Br Med J [online] 1963 Nov 16, 2(5367):1230-1233 [viewed 01 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1873329
  5. CHUNG EK. Digitalis intoxication. Postgrad Med J [online] 1972 Mar, 48(557):163-179 [viewed 01 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2495199
  6. SUCU M, DAVUTOGLU V, OZER O. Electrical cardioversion Ann Saudi Med [online] 2009, 29(3):201-206 [viewed 02 July 2014] Available from: doi:10.4103/0256-4947.51775