Interference dissociation

Cardiovascular

Clinicals - 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.
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.
Asymptomatic 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 Asymptomatic
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
Exertional dyspnea/ Chest pain 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 Exertional dyspnea/ Chest pain
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
Light-headedness/ Syncope 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. Light-headedness/ Syncope
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.
Palpitations 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 Palpitations
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
Fatigue, malaise 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. Fatigue, malaise
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.

Clinicals - Examination

Fact Explanation
Tachycardia/Bradycardia Pulse rate could be either fast or slow depending on the arrhythmia Tachycardia/Bradycardia
Pulse rate could be either fast or slow depending on the arrhythmia
Irregularity in pulse 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. Irregularity in pulse
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.
Hypotension Blood pressure could be low in ventricular tachycardia Hypotension
Blood pressure could be low in ventricular tachycardia
Intermittent Cannon Wave in Jugular venous pulse Intermittent cannon a waves can occur when atria and ventricles contract simultaneously Intermittent Cannon Wave in Jugular venous pulse
Intermittent cannon a waves can occur when atria and ventricles contract simultaneously
Variable intensity of the first heart sound This occurs due to atrioventricular dyssynchrony Variable intensity of the first heart sound
This occurs due to atrioventricular dyssynchrony

Investigations - Diagnosis

Fact Explanation
Electrocardiogram 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. Electrocardiogram
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.
serum Digoxin level Digoxin toxicity can cause various conduction abnormalities, therefore to exclude toxicity, serum Digoxin level is done serum Digoxin level
Digoxin toxicity can cause various conduction abnormalities, therefore to exclude toxicity, serum Digoxin level is done
Exercise ECG sometimes, the arrhythmias are apparent only when the heart is exerted, therefore, this is done when the diagnosis is not apparent on resting ECG. Exercise ECG
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 Atrioventricular dissociation can be easily detected using different echocardiographic modalities like M-mode, mitral valve movement, flow Doppler, or tissue Doppler Echocardiography
Atrioventricular dissociation can be easily detected using different echocardiographic modalities like M-mode, mitral valve movement, flow Doppler, or tissue Doppler

Investigations - Management

Fact Explanation
Electrocardiography (ECG) To assess for development of any other life threatening arrhythmias such as complete heart block, and to see the arrhythmias induced by drug therapy. Electrocardiography (ECG)
To assess for development of any other life threatening arrhythmias such as complete heart block, and to see the arrhythmias induced by drug therapy.
Echocardiography To assess for ejection fraction, for the possibility of congestive cardiac failure as consequence later Echocardiography
To assess for ejection fraction, for the possibility of congestive cardiac failure as consequence later
Venography 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. Venography
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.
Renal function tests including estimated glomerular filteration rate, serum creatinine, blood urea nitrogen To assess renal function prior anesthesia Renal function tests including estimated glomerular filteration rate, serum creatinine, blood urea nitrogen
To assess renal function prior anesthesia
Full blood count To exclude anemia. Full blood count
To exclude anemia.
Coagulation studies To exclude any coagulopathy. Coagulation studies
To exclude any coagulopathy.

Management - Supportive

Fact Explanation
Acute management of in an unstable patient. 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 Acute management of in an unstable patient.
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
Acute management with Pharamacological therapy Anticholinergic agents Competitive inhibitor at autonomic, postganglionic, and cholinergic receptors such as Atropine,Sulfate Increases heart rate causing increase in cardiac output. Acute management with Pharamacological therapy
Anticholinergic agents Competitive inhibitor at autonomic, postganglionic, and cholinergic receptors such as Atropine,Sulfate Increases heart rate causing increase in cardiac output.
Dietary management No special diets required. low-cholesterol diets, low-salt diets both recommended if in heart failure. Dietary management
No special diets required. low-cholesterol diets, low-salt diets both recommended if in heart failure.
Activity Increased sympathetic tone during strenuous physical exertion can precipitate many arrhythmias, Therefore it's better avoided Activity
Increased sympathetic tone during strenuous physical exertion can precipitate many arrhythmias, Therefore it's better avoided
Patient education 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. Patient education
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.
Patient identification When a patient presents with syncope, cardiac arrest, patient identification with a bracelet/ diagnosis card is helpful for further management Patient identification
When a patient presents with syncope, cardiac arrest, patient identification with a bracelet/ diagnosis card is helpful for further management

Management - Specific

Fact Explanation
Pharamacological therapy Anticholinergic agents Competitive inhibitor at autonomic, postganglionic, and cholinergic receptors such as Atropine Sulfate Increases heart rate, causing increase in cardiac output. Pharamacological therapy
Anticholinergic agents Competitive inhibitor at autonomic, postganglionic, and cholinergic receptors such as Atropine Sulfate Increases heart rate, causing increase in cardiac output.
Pacemaker implantation Permanent pacing with pacemaker implantation may be necessary if there's in adequate response to drugs Pacemaker implantation
Permanent pacing with pacemaker implantation may be necessary if there's in adequate response to drugs

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