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Albany Medical Review

EKG Case - 64 year old male with chest pain

Jason Vachon, MD

History of Present Illness

The patient is a 64 year old obese male who presented to the emergency room after developing severe chest pain.  The pain was localized to his left upper chest, with a pressure-like quality.  He did experience some dyspnea with the pain but did not have any diaphoresis or radiation of the pain.  Overall, the pain lasted for approximately one hour and had resolved by the time he arrived in the emergency department.  His past medical history was significant for coronary artery disease with a bypass graft performed in the late 1980s. His EKG done in the emergency department, and showed the following.

What does this electrocardiogram (ECG) demonstrate?

Discussion

This ECG shows a 2nd degree AV block, specifically a Wenckebach type block, or Mobitz I, in which the electrical conduction from the atria to the ventricles is intermittently interrupted.  The Wenckebach variety of 2nd degree block is characterized by a progressive prolongation of the PR interval from beat to beat, until there is a P wave with total failure to conduct to the ventricle, leading to a “dropped” beat.   Most Wenckebach blocks tend to be vagally mediated rather than due to a structural abnormality.  Most commonly, this is due to extra action from the parasympathetic system, seen in patients who are well trained athletes or with excess levels of a cardiac glycoside, such as digoxin.  Beta blockers and calcium channel blockers also can be associated with this block.  Other possible causes for this type of block include; age related fibrosis of the electrical conducting system, valvular heart disease, and heart surgery (especially in the area of the septum).             

Patients suffering from acute ischemia may also develop Wenckebach heart block.  Ischemia of the atrioventricular (AV) node is the typical mechanism and most commonly is associated with inferior myocardial infarctions.  Wenckebach blocks tend to be transient and regularly resolve without intervention.  It is uncommon for them to progress to a higher degree of heart block.  This is in contrast to the Mobitz II block which has a much greater propensity toward development of complete heart block.

The location of the lesion causing the block can occasionally be determined by looking at the QRS complex.  A narrow QRS indicates the block originates in the AV node whereas a widened QRS suggests infranodal pathology. The etiology of this patient’s block may have been ischemic, given his history of coronary artery disease and presentation.  After this initial EKG, his rhythm converted to a 1st degree sinus block.

REFERENCES

  1. Andreoli, Thomas, Charles Carpenter, Robert Griggs, and Joseph Loscalzo, eds. Cecil Essentials of Medicine. 6th Ed. Philadelphia, PA: WB Saunders Company,

  2. Dubin, Dale. Rapid Interpretation of EKG's. 6th ed. Tampa, FL: Cover Inc, 2000.

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