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Alternation of atrial cycle length in supraventricular tachycardia
Insights
This study presents nine cases of alternating atrial cycles during supraventricular tachycardia (SVT), with three linked to digitalis toxicity. These findings offer insights into SVT mechanisms and digitalis effects on cardiac rhythm.
Area of Science:
- Cardiology
- Electrophysiology
- Pharmacology
Background:
- Supraventricular tachycardia (SVT) can exhibit complex atrial cycle alternations.
- Digitalis toxicity is a known factor that can influence cardiac arrhythmias.
- Understanding the mechanisms of SVT is crucial for effective patient management.
Purpose of the Study:
- To describe and analyze cases of atrial cycle alternation during SVT.
- To investigate the role of digitalis toxicity in these specific cases.
- To explore the underlying electrophysiological mechanisms of observed phenomena.
Main Methods:
- Case series presentation of nine patients with SVT and atrial cycle alternation.
- Detailed analysis of electrocardiographic findings, including P wave morphology and atrial rates.
- Exclusion of ventriculophasic causes for the observed alternations.
Main Results:
- Nine cases of atrial cycle alternation during SVT were identified.
- Three cases were clearly associated with digitalis toxicity.
- Observed features included absence of 1/1 conduction, upright P waves in Lead II, and atrial rates from 156-218 bpm.
- Upon resolution of alternation, the atrium reverted to the longest preceding cycle length.
Conclusions:
- Atrial cycle alternation during SVT is a notable phenomenon, potentially linked to digitalis toxicity.
- The findings suggest specific electrophysiological properties of the atria during certain SVTs.
- Further investigation into the functional anatomy of SVT mechanisms is warranted.
Abstract:
Nine cases of alternation of the atrial cycles during supraventricular tachycardia are presented, three of which were manifestly due to digitalis toxicity. They presented the following features: absence of 1/1 conduction, upright P waves in Lead II, atrial rates of 156-218. When alternation disappeared, the atrium adopted the longest of the previously inscribed cycles. A ventriculophasic cause was excluded. The possible mechanisms are discussed in terms of the known functional anatomy of the various forms of SVT.