Key result
AVNRT episodes linked to greater ST-segment depression versus sinus rhythm, correlating with tachycardia cycle length.
Why the study?
ST-segment depression is often observed during paroxysmal narrow QRS complex tachycardia in young, healthy people, but its mechanisms remain not fully understood.
What is the mechanism of ST-segment depression during atrioventricular nodal reentrant tachycardia (AVNRT)?
Observational (n=50)
No
What is the mechanism of ST-segment depression during atrioventricular nodal reentrant tachycardia (AVNRT)?
Absolute Event Rate: 0.163% vs 0.081%
p-value: p=0.000
ST-segment depression during AVNRT is likely caused by the overlap of the QRS complex on the preceding T wave rather than myocardial ischemia, and its degree correlates with tachycardia cycle length.
ST depression during AVNRT may reflect rate-related overlap rather than ischemia; hypothesis-generating and should not yet change practice.
BACKGROUND: The ST-segment is part of the electrocardiogram and physiologically, it forms an isoelectric line. The ST-segment depression is often observed in young, healthy people with paroxysmal tachycardia with narrow QRS complexes. In this group of patients, the 'mysterious tachycardia-induced ST-segment depression', 'subendocardial myocardial ischemia' and other not fully understood terms are used to explain this phenomenon. OBJECTIVES: To assess the presence and possible mechanisms of ST-segment depression during atrioventricular nodal reentrant tachycardia (AVNRT) in patients undergoing radiofrequency (RF) ablation of the underlying arrhythmia. MATERIAL AND METHODS: The study included 50 patients (35 women and 15 men) aged about 49 years with clinically relevant paroxysmal narrow QRS complex tachycardia. During electrophysiological study (EPS), all patients had measured QRS components - QR, RS and RJ during the tachycardia and during the sinus rhythm. All of the measurements were done in lead V5. RESULTS: There was a statistically significant difference in cycle length during sinus rhythm and tachycardia (707.0 ±137.8 ms compared to 327.5 ±29.1 ms, p = 0.000), the RJ component (0.819 ±0.381 mV compared to 0.878 ±0.376 mV, p = 0.003) and the difference RJ-QR (0.081 ±0.083 mV compared to 0.163 ±0.108 mV, p = 0.000). The differences in RS and QR components during sinus rhythm and tachycardia did not reach the statistical significance. The difference RJ-QR during tachycardia correlated negatively with tachycardia cycle length (R = -0.39, p = 0.0049). The tachycardia cycle length correlated positively with the age of the studied patients (R = 0.28, p = 0.043). CONCLUSION: In patients with AVNRT, there is a ST-segment depression during the episodes of tachycardia and the degree of this change is related to tachycardia cycle length. The most probable explanation of the ST-segment depression is the overlap of the QRS complex on the preceded T wave. Some intrinsic properties of individual electrocardiogram (ECG) also influence this phenomenon. The ischemic origin of the presented ST-segment change can be excluded.
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Mercik et al. (2021) conducted an observational in Atrioventricular nodal reentrant tachycardia (AVNRT) (n=50). Atrioventricular nodal reentrant tachycardia (AVNRT) vs. Sinus rhythm was evaluated on RJ-QR difference (mV) (p=0.000). During AVNRT episodes, patients exhibited significant ST-segment depression compared to sinus rhythm (RJ-QR difference 0.163 mV vs 0.081 mV, p=0.000), which correlated with tachycardia cycle length.
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