Background Anti-tachycardia pacing (ATP) is a pain-free alternative to defibrillation shock for monomorphic ventricular tachycardia (VT). Intrinsic ATP (iATP) is a novel algorithm of auto-programmed ATP. However, the advantage of iATP over conventional ATP in clinical cases is still unknown. Case summary A 49-year-old man with no significant past medical history was transferred to our institution with sudden onset fatigue from working on a farm. A 12-lead electrocardiogram showed monomorphic sustained wide QRS tachycardia with a right bundle branch block pattern and superior axis deviation with a cycle length of 300ms. Sustained monomorphic ventricular tachycardia (VT) originating from the left ventricle due to underlying vasospastic angina was diagnosed by contrast-enhanced cardiac MRI, coronary angiography and the acetylcholine stress test, and ICD implantation was performed. Nine months later, a clinical VT episode with a cycle length of 300 ms was observed, which could not be terminated by three sequences of conventional burst pacing. VT was finally terminated by a third iATP sequence without any acceleration. Discussion Although standard burst pacing by conventional ATP reached the VT circuit, it failed to terminate the VT. Using the post-pacing interval, iATP automatically calculated the appropriate number of S1 pulses required to reach the VT circuit. In iATP, the S2 pulses are delivered with a calculated coupling interval based on the estimated effective refractory period during tachycardia. In this case, iATP might have led to less aggressive S1 stimulation followed by aggressive S2 stimulation, which probably helped terminate the VT without any acceleration.

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It has been found that the assessment of coronary artery lesions using the fractional flow reserve and instantaneous flow reserve measurements reduces the incidence of further cardiovascular events. Here, we investigated differences in the coronary flow velocity and resistance within the analysis interval between the instantaneous flow reserve (iFR) and the intracoronary electrocardiogram (IC-ECG)-triggered distal/aortic pressure (Pd/Pa) ratio (ICE-T). Thirty-three consecutive patients with stenoses that required coronary flow measurement were enrolled. ICE-T was defined as the average Pd/Pa ratio in the period corresponding to the isoelectric line of the IC-ECG. The index value, flow velocity, and intracoronary resistance during the analysis intervals of the iFR and ICE-T, both at rest and under hyperemia, were compared. The index value and intracoronary resistance of the ICE-T were found to be significantly lower, while the flow velocity was significantly higher, than those of the iFR (P < 0.001), and all fluctuations in ICE-T values were also significantly smaller than those in the iFR.In conclusion, the ICE-T is theoretically superior to pressure-dependent indices for analyzing phases with low and stable resistance, without an increase in invasiveness.

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