The third degree atrioventricular block may rarely be asymptomatic, more often having hypoperfusion- related symptoms, such as fatigability, chest pain, dyspnea, dizziness, irritability, apathy, inability to concentrate, forgetfulness, confusion. In severe cases, syncope and sudden death occur.

Facing a patient with associated symptoms like severe chest pain, nausea, dyspnea and diaphoresis, the clinician should consider an acute myocardial infarction as the cause of the complete heart block [1]. On the other hand, chronic cardiac patients undergo different kinds of treatment that have a potential to induce heart block: digitalis, calcium channel blockers, beta blockers and medication that can induce hyperkalemia, like angiotensin-converting enzyme inhibitors and angiotensin receptor blockers.

In addition to symptoms caused by the heart block, patients may have complaints linked to the cause of the block, like ischemia, myocarditis, hypothyroidism, cardiomyopathy, hypothermia and electrolyte disturbances [1]. Children with congenital third degree atrioventricular block may be symptomatic from birth [2].

In a patient with very low heart rate, the stimulus probably originates in the ventricles and is not due to a junctional pacemaker thus having a poor prognosis [3].

• Fatigue

  These symptoms include fatigue, dyspnea, dizziness and syncope. [healio.com]

  These may include chronic fatigue because of a lower than normal heart rate, syncope, palpitation, or even nightmares. Complete heart block can be found in a number of different situations in pediatric patients. [pediatricheartspecialists.com]

  It may be due to progressive fatigue of AV nodal cells as per Mobitz I (e.g. secondary to increased vagal tone in the acute phase of an inferior MI). [lifeinthefastlane.com]

  In these situations, symptoms include the following: Fatigue Dizziness Impaired exercise tolerance Chest pain Patients with narrow complex escape rhythms (eg, those whose escape rhythm occurs above the His bundle) are more likely to have minimal symptoms [emedicine.medscape.com]

• Falling

  He was not injured in the fall, but the paramedics noted a slow pulse. He denied significant medical history. [ecgguru.com]

  Administer 0.5mg of Atropine IV if heart rate falls and patient is symptomatic. Repeat every 3-5 minutes as needed, until a satisfactory rate is obtained or until 3mg is reached. Use transcutaneous cardiac pacing (TCP) if available. [mstcparamedic.pbworks.com]

  These delays fall into categories of first, second, and third-degree blocks. Third-degree blocks are also known as complete heart block. [ncbi.nlm.nih.gov]

  Falling Predector Frame Slider Anti-Crash Cap fit for Yamaha MT07 FZ07 14-16 “Another reason to love Dilly’s Tree House is that it is designed to be used for about 10-15 minutes, three times a week. [terridsphotography.com]

  Complications Complications include the following: Sudden cardiac death due to asystole Syncope Musculoskeletal injuries secondary to fall after syncope. [emedicine.com]

• Congestive Heart Failure

  We performed multivariate analysis adjusting for coronary artery disease, congestive heart failure, smoking, and hyperlipidemia. Continuous and binary variables were analyzed using chi2 and Fisher exact tests. [ncbi.nlm.nih.gov]

  Signs of congestive heart failure as a result of decreased cardiac output may be present and may include the following: Tachypnea or respiratory distress Rales Jugular venous distention Patients may have signs of hypoperfusion, including the following [emedicine.medscape.com]

  Permanent insertion of a pacemaker may be recommended for individuals with Stokes-Adams attacks, congestive heart failure or significant cardiomegaly, or infants with a ventricular rate of less than 55 beats per minute. [rarediseases.org]

• Relapsing Polychondritis

  Polychondritis (see Relapsing Polychondritis, [[Relapsing Polychondritis]]) Rheumatoid Arthritis (RA) (see Rheumatoid Arthritis, [[Rheumatoid Arthritis]]) Scleroderma (see Scleroderma, [[Scleroderma]]) Toxic Grayanotoxin (“Mad” Honey) Nerium Oleander [mdnxs.com]

  polychondritis, rheumatoid arthritis, scleroderma Infiltrative processes: Amyloidosis, sarcoidosis, tumors, Hodgkin disease, multiple myeloma Neuromuscular disorders: Becker muscular dystrophy, myotonic muscular dystrophy Ischemic or infarctive causes [emedicine.com]

• Unconsciousness

  […] techniques -- pt. 8.5: Established renal failure -- Sect. 9: The neurological system -- pt. 9.1: Anatomy and physiology -- pt. 9.2: Neurological monitoring -- pt. 9.3: Sleep disturbance -- pt. 9.4: Agitation, confusion, and delirium -- pt. 9.5: The unconscious [worldcat.org]

  Individuals with complete heart block may experience episodes of unconsciousness (syncope), breathlessness, lack of energy (lethargy), and/or low blood pressure (hypotension). [rarediseases.org]

  A particularly severe form of heart block is stokes-adams disease, in which sudden unconsciousness results from the slowed heartbeat. It may be accompanied by convulsions. [medical-dictionary.thefreedictionary.com]

• Exertional Dyspnea

  A 48-year-old man was admitted with exertional dyspnea. An ECG on admission revealed third-degree atrioventricular block (Figure 1). [ahajournals.org]

• Skipped Beats

  Finally, an atrial impulse is blocked in the AV node and fails to conduct to the ventricles, leading to a skipped beat. [washingtonhra.com]

  First-degree heart block involves minor heartbeat disruptions, such as skipped beats. It is the least serious type of heart block, and it does not generally require treatment. [medicalnewstoday.com]

  Your heart may beat slowly, or it may skip beats. Heart block may resolve on its own, or it may be permanent and require treatment. There are three degrees of heart block. [medlineplus.gov]

  For 1st-degree block, conduction is slowed without skipped beats. All normal P waves are followed by QRS complexes, but the PR interval is longer than normal ( 0.2 sec). [merckmanuals.com]

• Slow Pulse

  He was not injured in the fall, but the paramedics noted a slow pulse. He denied significant medical history. [ecgguru.com]

• Irregular Heart Rhythm

  Second-degree heart block has a slower – and sometimes irregular – heart rhythm. Not all signals reach the ventricles and some heart beats are dropped. Third-degree heart block (complete atrioventricular block) is the most severe form. [heartandstroke.ca]

• Dizziness

  Sign in Published on Nov 25, 2015 Complete heart block (also called third-degree heart block) is a type of abnormal heart rhythm (cardiac arrhythmia) that can cause dizziness, confusion and sometimes breathlessness. [youtube.com]

  This 84-year-old man called 911 because he felt dizzy and fell. He was not injured in the fall, but the paramedics noted a slow pulse. He denied significant medical history. [ecgguru.com]

  These symptoms include fatigue, dyspnea, dizziness and syncope. [healio.com]

  In some cases complete heart block can lead to episodes of feeling dizzy or collapsing. It can make you extremely tired, confused or breathless. It may also cause fluid to build up in your body. [bhf.org.uk]

• Confusion

  Sign in Published on Nov 25, 2015 Complete heart block (also called third-degree heart block) is a type of abnormal heart rhythm (cardiac arrhythmia) that can cause dizziness, confusion and sometimes breathlessness. [youtube.com]

  You will also have the following with this rhythm: P-waves & R-wave will be IRREGULAR PR intervals ABNORMAL Missing QRS complex CYCLIC 2 nd Degree Type 2 Mobitz II Many people like to confuse this rhythm with a Wenckebach and third degree. [registerednursern.com]

  Differential diagnosis Complete heart block should not be confused with: High grade AV block : A type of severe second degree heart block with a very slow ventricular rate but still some evidence of occasional AV conduction. [lifeinthefastlane.com]

• Altered Mental Status

  mental status Hypotension Lethargy In patients with concomitant myocardial ischemia or myocardial infarction (MI), corresponding signs such as the following may be evident on examination: Signs of anxiety (eg, agitation, unease) Diaphoresis Pale or pasty [emedicine.medscape.com]

  Patients may also exhibit tachypnea or respiratory distress, rales, jugular venous distention, altered mental status, hypotension, and lethargy; signs of anxiety such as agitation or unease, diaphoresis, pale or pasty complexion and tachypnea. [alivecor.com]

  Particularly with heart rates below 40/min, patients might also demonstrate findings consistent with decompensated heart failure, respiratory distress, and hypoprofusion such as diaphoresis, tachypnea, altered mental status, retraction, cool skin, and [ncbi.nlm.nih.gov]

  N/A If patient has altered mental status, hypotension, shortness of breath, or chest pain likely due to AV block, place transcutaneous pacer pads and provide supplemental oxygen. [cancertherapyadvisor.com]

• Dysautonomia

  The unopposed parasympathetic tone in patients with dysautonomia may make them susceptible to bradycardia and atrioventricular block. [ncbi.nlm.nih.gov]

  […] atrioventricular block and asystole in a child with familial dysautonomia", abstract "An 11-year-old boy with familial dysautonomia presented with palpitations. [scholars.northwestern.edu]

• Vertigo

  […] sedation and analgesia -- Monitoring the emergency patient -- Shock -- Brain resuscitation -- Adult resuscitation -- Fever in the adult patient -- Weakness -- Cyanosis -- Syncope -- Depressed consciousness and coma -- Confusion -- Seizures -- Dizziness and vertigo [worldcat.org]

The physical examination of third degree atrioventricular block patients will often show signs of decreased perfusion and those of underlying disease.

Inspection may show turgescent jugular veins and cannon " a" waves caused by the contraction of the right atrium against the closed tricuspid valve, peripheral edema or skin rashes if the cause of the block is Lyme disease, endocarditis, or rheumatic fever.

Palpation may reveal hepatomegaly in heart failure patients, while auscultation reveals pulmonary rales, variable first heart sound, murmurs caused by mitral or aortic calcification or cardiomyopathies and a low heart rate. Arterial pressure may be low.

Blood workup should include a complete blood cell count (in order to diagnose infection and anemia), renal function, electrolytes (especially potassium, given that hyperpotassemia is a cause of third degree atrioventricular block by itself), prothrombin time, activated partial thromboplastin time (having in mind that emergency cardiostimulation may be necessary) and digoxin level. If myocarditis is suspected, every effort should be put into determining its cause: human immunodeficiency virus infection, Lyme disease, adenovirus or enterovirus infection.

A chest radiograph may offer clues about the cardiac silhouette and possible associated pneumonia. Transthoracic echocardiography may find aortic and mitral calcification or abscesses, hypertrophic cardiomyopathy and left ventricle systolic function.

The diagnosis is established using a 12 lead electrocardiogram, showing complete atrioventricular dissociation [4], with constant R-R intervals and either narrow (<120 msec) or wide ventricular complexes, depending on the site of the stimulus: atrioventricular junction, His bundle or ventricular myocardium. The atrial rate is faster than the ventricular one, which is usually 30-40 beats per minute. The electrocardiogram may also show ischemia, in which case cardiac enzymes should be measured and coronarography should be performed. Anterior myocardial infarctions complicated with complete atrioventricular block have higher instability risk [2]. A complete atrioventricular block is the most frequent bradyarrhythmia in myocardial infarctions [5].

If symptoms are intermittent and the electrocardiogram shows no abnormalities when the patient presents, an ambulatory monitoring or loop recorder is indicated [6] [7]. Furthermore, an electrophysiological study may be useful in cases where the origin of the stimulus is uncertain or in cases where symptoms seldom occur [8].

Other tests, like tilt table testing and carotid sinus massage, are to be performed in cases where the more plausible diagnosis is reflex syncope, not intermittent third degree atrioventricular block. If a patient only has symptoms after performing an effort, exercise testing is called for.

• Wide QRS Complex

  The escape rhythm may have narrow or wide QRS complexes, depending on from where the impulses are discharged and whether there is concomitant bundle branch block. [ecgwaves.com]

  If the block is lower in the AV node, a ventricular rhythm may exist, with wide QRS complexes. 3 Atrioventricular Block: Complete Heart Block Rate: Atrial rate will be independent of ventricular rate. V-rate depends on escape. [ems12lead.com]

  Therefore in the presence of complete AV block, narrow QRS complexes indicate an AV junctional location of the block, but wide QRS complexes may be the result of bilateral bundle branch block or AV junctional block with a bundle branch block 3. [en.my-ekg.com]

  The wide QRS complexes have a strong left axis deviation, which could support the argument for idioventricular escape rhythm. What do you think? Please comment below. [ecgguru.com]

• Trypanosoma Cruzi

  cruzi Varicella-Zoster Virus (see Varicella-Zoster Virus, [[Varicella-Zoster Virus]]) Infiltration Amyloidosis (see see Amyloidosis, [[Amyloidosis]]) Hodgkin’s Disease see Hodgkin’s Disease, [[Hodgkins Disease]]) Multiple Myeloma (see Multiple Myeloma [mdnxs.com]

  cruzi infection, [7] rheumatic fever, myocarditis, Chagas disease, Aspergillus myocarditis, varicella-zoster virus infection, [8] valve ring abscess Rheumatic diseases: Ankylosing spondylitis, Reiter syndrome, relapsing polychondritis, rheumatoid arthritis [emedicine.com]

• Atrioventricular Dissociation

  Electrocardiogram Findings of Complete AV Block Complete AV block: Atrioventricular dissociation, P waves (red arrows) are not followed by QRS complexes PP and RR intervals are regular. P waves bear no constant relation to QRS complexes. [en.my-ekg.com]

  The electrocardiographic expression is complete atrioventricular dissociation with narrow or wide ventricular complexes and a decreased ventricular rhythm. The condition may be permanent or intermittent, depending on the etiology. [symptoma.com]

  As the name implies, no impulses from the SA node get conducted to the ventricles, and this leads to a complete atrioventricular dissociation. [ncbi.nlm.nih.gov]

  dissociation (2) occurs; atria and ventricles beat independently. heart block ( hahrt blok ) impairment of conduction of an impulse in heart excitation; often applied specifically to atrioventricular block. [medical-dictionary.thefreedictionary.com]

  See the Medscape Drugs & Diseases article Atrioventricular Dissociation for more detailed information on this topic. [emedicine.medscape.com]

• Cannon A-Waves

  Careful examination of the neck veins can often show evidence of cannon ‘a’ waves. A variable intensity S 1 may be heard on auscultation. In addition, the pulse rate may be slow. [emedicine.medscape.com]

  Inspection may show turgescent jugular veins and cannon " a" waves caused by the contraction of the right atrium against the closed tricuspid valve, peripheral edema or skin rashes if the cause of the block is Lyme disease, endocarditis, or rheumatic [symptoma.com]

  An inability of the patient to follow instructions, crackles on pulmonary exam and cannon A waves observed within jugular venous pulsations may indicate a clinically severe AV block. [cancertherapyadvisor.com]

  JVP exam often demonstrates cannon A-waves as the atria and ventricles contract simultaneously, which results in significant pushing of the blood against the AV valve. Thus a very large pressure wave runs up against the vein. [ncbi.nlm.nih.gov]

1. Barra S, Providencia R, Paiva L, et al. A review on advanced atrioventricular block in young or middle aged adults. Pacing Clin Electrophysiol. 2012;35(11):1395–1405.
2. Hayden GE, Brady WJ, Pollack M, et al. Electrocardiographic manifestations: Diagnosis of atrioventricular block in the emergency department. J Emerg Med. 2004;26(1):95–106.
3. Ufberg JW, Clark JS. Bradydysrhythmias and atrioventricular conduction blocks. Emerg Med Clin N Am. 2006;24(1):1–9.
4. Swart G, Brady WJ, DeBehnke DJ, Ma OJ, Aufderheide TP. Acute myocardial infarction complicated by hemodynamically unstable bradyarrhythmia: prehospital and ED treatment with atropine. Am J Emerg Med. 1999;17(7):647–652.
5. Deal N. Evaluation and management of bradydysrhythmias in the emergency department. Emerg Med Pract. 2013;15(9):1–15.
6. Bergfeldt L, Edvardsson N, Rosenqvist M, et al. Atrioventricular block progression in patients with bifascicular block assessed by repeated electrocardiography and a bradycardia-detecting pacemaker, Am J Cardiol. 1994;74:1129-1132.
7. Brignole M, Sutton R, Menozzi C, et al. Early application of an implantable loop recorder allows effective specific therapy in patients with recurrent suspected neurally mediated syncope, Eur Heart J. 2006;27:1085-1092.
8. Moya A, Garcia-Civera R, Croci F, et al. Diagnosis, management, and outcomes of patients with syncope and bundle branch block, Eur Heart J. 2011;32:1535-1541.