Case 9: A 54 year old woman undergoing chemotherapy for bronchio-alveolar carcinoma. Two years previous underwent emergency pericardiocentesis for cardiac tamponade (malignant effusion). Complaining of rapid palpitations.
Questions For Thought:
1. What is the mechanism of the fast rhythm?
2. Why do you think she has it?
Following is the ECG of same patient with normal heart rate,
Its Supraventricular tachycardia and its not sure by the history and ECG alone that why she has it, Read the follow up below for explanation.
The patients blood pressure is 95/60 during the tachycardia, but there is no paradoxical pulse and though there are prominent A-waves on the examination of the jugulars, the jugular pressure is not felt to be elevated; the heart sounds are loud and the patient is not particularly dyspneic. It is therefore less likely that this is sinus tachycardia due to tamponade, something the patient remembers very well from two years earlier.
This ECG is a regular narrow complex tachycardia at a rate of 134 bpm. Determining whether there are identifiable P-waves is challenging. The differential diagnosis includes primarily sinus tachycardia, atrial flutter with 2:1 AV conduction, atrial tachycardia or a reentrant supraventricular tachycardia (SVT). As there are no clear P-waves or flutter waves, reentrant SVT tops the list.
Look at the comparison between the V1 and V5 QRS complexes of the tachycardia ECG with those same leads of the sinus rhythm ECG. Note what almost appears to be an incomplete right bundle branch block pattern (rSr' in V1) during the tachycardia. It isn't present in the slower ECG. It is possible that this could represent a rate-related minor conduction delay but it is more likely caused by a retrogradely generated P-wave that ends just after the QRS, creating this pseudo-incomplete RBBB. In fact, this pattern is often seen in SVT due to so-called AV node reentry. It is also visible in V5. SVT of this type is the most common of the recurrent reentrant SVTs, and it is due to the presence of dual AV nodal pathways.
There are non-specific ST-T changes in this ECG. This is common with rapid tachycardias and has little diagnostic significance. It certainly does not indicate myocardial iscemia. The q-wave isolated to lead III and the T-wave inversion seen only in that lead is normal. Note that it is also seen in the sinus rhythm ECG.
As it turns out, this patient has been experiencing palpitations of this type since she was 14 years old. She was told during her youth that they were due to anxiety. The SVT, therefore, is longstanding and has nothing to do with her malignancy diagnosis or her previously diagnosed pericardial disease. Because she was now having episodes several times per day, she was taken to the electrophysiology laboratory where RF ablation was successful in eliminating the slow version of the dual pathways and SVT was fixed.
Happy Learning :-)
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