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Sinoatrial Block

Blocks Sinoatrial

Sinoatrial block, also known as sinoatrial exit block, is a cardiac abnormality in which inability of the heart to conduct impulses from the sinoatrial node leads to a range of arrhythmias and associated symptoms. The diagnosis rests on clinical findings and electrocardiography.


Presentation

Sinoatrial (SA) block is one of the forms of sinus node dysfunction (SND), and its main pathological entities, bradycardia (and less commonly tachycardia) cause low cardiac output and the appearance of various symptoms [1] [2] [3]. Patients can be asymptomatic for a prolonged period of time, but the unpredictable and often sudden appearance of dizziness, palpitations, vertigo and syncope without an identifiable cause are main clinical manifestations of SA block [4] [5]. Angina, dyspnea, fatigue, lethargy and premature mental incapacity may point to initial stages of congestive heart failure, which may occur in the setting of profound arrhythmias [4]. In addition to bradycardia, numerous forms of tachyarrhythmia appear in diseases of the SA node, including SA block, most common entities being supraventricular tachycardias - atrial flutter and atrial fibrillation [6]. In fact, tachycardia seems to be responsible for the onset of palpitations and heart failure, whereas hypotension, syncope, and weakness arise due to bradycardia [6]. Paradoxically, atrial fibrillation can reduce the burden of symptoms in patients with persistent bradycardia, as it directly increases heart rate [6]. In rare cases, cardiac arrest and death have been noted, while other generalised symptoms include slurred speech, irritability, and poor infant feeding.

Chest Discomfort
  • Abstract A 59 year old woman presented with acute onset of fever, chills, diaphoresis, vague chest discomfort, and was found to be hypotensive and tachypnoeic.[ncbi.nlm.nih.gov]
Chills
  • Abstract A 59 year old woman presented with acute onset of fever, chills, diaphoresis, vague chest discomfort, and was found to be hypotensive and tachypnoeic.[ncbi.nlm.nih.gov]
Sleep Apnea
  • However, in cases where dizziness and near syncope due to a sinus node dysfunction are found together with clinical characteristics of a sleep apnea-hypopnea syndrome (SAHS), screening for sleep apnea would be prudent before deciding for a pacemaker.[ncbi.nlm.nih.gov]
Heart Disease
  • Twenty-one patients had organic heart disease; in the remaining ten signs of underlying heart disease were not present. Nineteen patients had dizziness or syncope.[ncbi.nlm.nih.gov]
  • Analysis of the survival curves shows that the excess mortality is caused by coexisting diseases, primarily coronary heart disease with previous myocardial infarction and valvular heart disease.[ncbi.nlm.nih.gov]
  • However, it always interferes with using an electrocardiogram to diagnose heart disease. Causes and Risk Factors Bundle branch block is a common disorder. It occurs in many medical conditions.[cedars-sinai.edu]
  • These medical conditions include: Heart failure Prior heart attack Heart valve abnormalities Heart valve surgery Congenital heart diseases Some medications or exposure to toxic substances Lyme disease Aging[hrsonline.org]
  • ICD-10-CM Codes › I00-I99 Diseases of the circulatory system › I30-I52 Other forms of heart disease › I49- Other cardiac arrhythmias › Other specified cardiac arrhythmias 2016 2017 2018 2019 Billable/Specific Code I49.8 is a billable/specific ICD-10-CM[icd10data.com]
Pulse Deficit
  • Abstract A 58-year-old man with variant angina who had no history suggestive of sinus node dysfunction experienced palpitation with pulse deficit after 8 days of diltiazem treatment, 240 mg per day.[ncbi.nlm.nih.gov]
Shoulder Pain
  • In the third patient, in addition to DPH which was administered for epileptic seizures, Carbamazepine was given for shoulder pain, then SA block occurred.[ncbi.nlm.nih.gov]
Suggestibility
  • METHODS AND RESULTS: The study included 300 patients (mean age 54 17 years; 130 women) with symptoms suggestive of arrhythmia who underwent Holter monitoring.[ncbi.nlm.nih.gov]
  • These findings suggested that increased vagal tone during expiration depressed conductivity in the SA junction to a greater degree than automaticity in the sinus node.[ncbi.nlm.nih.gov]
  • Abstract A 58-year-old man with variant angina who had no history suggestive of sinus node dysfunction experienced palpitation with pulse deficit after 8 days of diltiazem treatment, 240 mg per day.[ncbi.nlm.nih.gov]
  • It is suggested that while in some cases sinoatrial block may be of physiological origin, it is more often due to sinoatrial disease.[ncbi.nlm.nih.gov]
  • Multiple, repetitive, low frequency deflections, with a cycle length ranging from 730 to 960 ms in Case 1 and 570 to 750 ms in Case 2, suggestive of sinus node electrograms, were recorded at a critical area at the junction between the superior vena cava[ncbi.nlm.nih.gov]
Altered Mental Status
  • In some people, they can cause fainting, altered mental status, chest pain, hypoperfusion, and signs of shock. They can also lead to cessation of the SA node and more serious dysrhythmias.[en.wikipedia.org]
Slurred Speech
  • In rare cases, cardiac arrest and death have been noted, while other generalised symptoms include slurred speech, irritability, and poor infant feeding.[symptoma.com]

Workup

A thorough patient history and a detailed physical examination are essential steps in making an initial diagnosis of an SA block. Severe bradycardia or other rhythm abnormalities, weak arterial pulses and hypotension can be observed during cardiac auscultation. When such findings are documented, electrocardiography (ECG) studies should be done. On the basis of ECG findings, SA block is classified into four subtypes [2] [3] [5] [6]:

  • Type 1 - Minimal prolongation of the SA node may either present with a normal ECG (1st-degree) or with intermittent failure of impulse conduction to the arterioventricular (AV) node (2nd-degree), manifesting as an occasional absence of P waves.
  • Type 2 - In 1st-degree type 2 SA block (also known as Wenckebach block), slowing of the impulse is noted before the onset of a blockade, which is seen on ECG as a decreasing P-P interval that ultimately causes joining of two P waves and a consequent pause. In 2nd-degree type 2 block, on the other hand, SA impulse blocks occur without slowing, but the pause is much greater and the appearance of grouped beats may be detected.
  • Type 3 - The definite absence of P waves, also known as sinus arrest, is the main feature of a complete SA block.

Because SA blocks present with various ECG manifestations, use of devices that ensure long-term monitoring of cardiac impulse conduction, as well as exercise testing and intracardiac electrophysiologic tests, are recommended when valid clinical criteria exist [2].

Suppression
  • One should note that diltiazem induces not only sinus node suppression and atrioventricular conduction disturbance, but also sinoatrial block.[ncbi.nlm.nih.gov]
  • In 1 of these 2 patients, overdrive suppression test revealed normal sinus node recovery time. In the third patient, in addition to DPH which was administered for epileptic seizures, Carbamazepine was given for shoulder pain, then SA block occurred.[ncbi.nlm.nih.gov]
  • However, they could be suppressed by spontaneous or paced atrial beats.[ncbi.nlm.nih.gov]
  • Limpitikul et al. (2014) showed that expression of mutated calmodulin suppressed Ca 2 /calmodulin mediated CDI in native Ca v 1.2 channels of ventricular myocytes.[doi.org]
Legionella Pneumophila
  • Her urine tested positive for Legionella pneumophila antigen serotype 1 and she improved with antibiotic therapy.[ncbi.nlm.nih.gov]
Prolonged PR Interval
  • This is different than a first-degree atrioventricular, or AV, block, which shows a prolonged PR interval. Second-degree sinoatrial exit block is categorized into type I and type II.[healio.com]
Sinus Arrest
  • A third degree sinoatrial block looks very similar to a sinus arrest. However, a sinus arrest is caused by a failure to form impulses. A third degree block is caused by failure to conduct them. The rhythm is irregular and either normal or slow.[en.wikipedia.org]
  • SA exit block, Sinus Arrest, AV Blocks and Escape Rhythms ECG EXERCISE 28.[slideshare.net]
  • The onset of 3rd degree SA block may produce long sinus pauses or sinus arrest (may lead to fatal asystole). Rhythm may be maintained by a junctional escape rhythm.[lifeinthefastlane.com]
  • Type 3 - The definite absence of P waves, also known as sinus arrest, is the main feature of a complete SA block.[symptoma.com]
  • SA block is included in a broader clinical scenario called “sick sinus syndrome” (SSS) that may consist in inappropriate sinus bradycardia, SA exit block or sinus arrest, prolonged sinus arrest with failing ectopic pacemaker, persistent atrial or atrioventricular[link.springer.com]

Treatment

  • The correlation between lithium treatment and tachyarrhythmias is discussed.[ncbi.nlm.nih.gov]
  • Sinus node modification with radiofrequency current has been used successfully as treatment for this arrhythmia. However, the electrophysiologic mechanisms leading to successful modification are not yet fully elucidated.[ncbi.nlm.nih.gov]
  • CONCLUSION: On diagnosing SAHS with an obstructive component in patients with symptomatic bradycardia and SA block, there is no primary need for a pacemaker, but rather for implementing treatment with nCPAP.[ncbi.nlm.nih.gov]
  • Treatment [ edit ] Emergency treatment consists of administration of atropine sulfate or transcutaneous pacing. References [ edit ] Bledsoe, Porter, Cherry (2009). Paramedic Care; Principles and Practice. New Jersey: Brady. ISBN 978-0-13-513702-4.[en.wikipedia.org]
  • All of these abnormalities resolved completely after antithyroid treatment. This course of events illustrates the profound effect of thyroid hormones on cardiac function.[ncbi.nlm.nih.gov]

Prognosis

  • KEYWORDS: Holter monitoring; Prognosis; Sinoatrial Wenckebach block[ncbi.nlm.nih.gov]
  • Prognosis of sinus node dysfunction is mixed; without treatment, mortality is about 2%/yr, primarily resulting from an underlying structural heart disorder. Each year, about 5% of patients develop AF with its risks of heart failure and stroke.[merckmanuals.com]

Etiology

  • Etiology SA block is uncommon and usually occurs transiently May occur in healthy clients with increased vagal tone or with vagal stimulation Found with CAD, inferior MI, myocarditis, heart failure, or disease of SA node Contributing medications (digoxin[ecgreview.weebly.com]
  • Etiology of sinus pauses and arrest: alteration in the impulse rate of the P cells. Therefore, the pause length is variable and not necessarily a multiple of the basic sinus rate.[hqmeded-ecg.blogspot.com]
  • While the etiology of this disease has remained obscure for long time, there is now strong evidence that loss-of-function of Ca v 1.3 and Ca v 3.1 channels underlie this pathology ( Strandberg et al., 2013 ).[doi.org]

Prevention

  • Bier block regional anesthesia by intravenous injection, used for surgical procedures on the forearm or the lower leg; performed in a bloodless field maintained by a pneumatic tourniquet that also prevents anesthetic from entering the systemic circulation[medical-dictionary.thefreedictionary.com]
  • Corrado D, Pelliccia A, Heidbuchel H et al (2010) Section of Sports Cardiology, European Association of Cardiovascular Prevention and Rehabilitation. Recommendations for interpretation of 12-lead electrocardiogram in the athlete.[link.springer.com]
  • Antiarrhythmic drugs may prevent paroxysmal tachyarrhythmias after pacemaker insertion. Theophylline and hydralazine are options to increase heart rate in healthy, younger patients who have bradycardia without syncope.[merckmanuals.com]
  • The National Heart, Lung, and Blood Institute (NHLBI) leads or sponsors many studies aimed at preventing, diagnosing, and treating heart, lung, blood, and sleep disorders.[nhlbi.nih.gov]
  • Benfotiamine prevents macro- and microvascular endothelial dysfunction and oxidative stress following a meal rich in advanced glycation end products in individuals with type 2 diabetes. Diabetes Care. 2006; 29(9):2064 – 71.[life-enhancement.com]

References

Article

  1. Choudhury M, Boyett MR, Morris GM. Biology of the Sinus Node and its Disease. Arrhythmia & Electrophysiology Review. 2015;4(1):28-34.
  2. Romandini A, Scappini L. Sinoatrial Exit Block. Clinical Cases in Cardiology. Springer International Publishing; 2015:255-264.
  3. Kramarz E, Makowski K. Clinical significance of second degree Wenckebach type sinoatrial block identified during Holter monitoring in patients with symptoms suggestive of arrhythmia. Europace. 2015;17(1):123-130.
  4. Vogler J1, Breithardt G, Eckardt L. Bradyarrhythmias and conduction blocks. Rev Esp Cardiol (Engl Ed). 2012;65(7):656-667.
  5. Porter RS, Kaplan JL. Merck Manual of Diagnosis and Therapy. 19th Edition. Merck Sharp & Dohme Corp. Whitehouse Station, N.J; 2011.
  6. Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson J, Loscalzo J. eds. Harrison's Principles of Internal Medicine, 18e. New York, NY: McGraw-Hill; 2012.

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Last updated: 2018-06-22 08:07