Background Beta-blockers and class 1A antiarrhythmics decrease the subaortic pressure gradient in hypertrophic obstructive cardiomyopathy. However, real-time monitoring of the pressure gradient transition during intravenous therapy, based on cardiac catheterization, has never been reported. Case Summary A 52-year-old man, with history of hypertension, was transferred to our hospital, complaining of angina. A 12-lead electrocardiogram showed diffuse ST- segment depression, and transthoracic echocardiography (TTE) revealed a thickened left ventricular outflow tract (LVOT) septum, resulting in LVOT obstruction which had never been diagnosed. Besides, severe mitral regurgitation (MR) due to systolic anterior motion was detected. Emergent cardiac catheterization revealed normal coronary arteries and severe MR. Simultaneous pressure measurements were taken at the ascending aorta (using a coronary catheter) and left ventricle (using a pressure wire). The subaortic systolic pressure gradient was 147 mmHg: 251 mmHg in the left ventricle and 104 mmHg in the aorta. Intravenous cibenzoline, following propranolol, was administered to ameliorate the pressure gradient, following which his chest pain disappeared immediately; the pressure gradient decreased to 13 mmHg. Further, severe MR was diminished. Oral bisoprolol and cibenzoline administration effectively stabilized his condition after catheterization. Discussion Monitoring the simultaneous pressure between the left ventricle and aorta with a pressure wire revealed drastic improvement in the subaortic systolic pressure gradient. Owing to the soft, fine structure, the pressure wire allowed recording of the subaortic pressure gradient stably with less frequent premature ventricular contractions. Furthermore, this method could decrease the burden of catheter-related complications by eliminating the need for multiple atrial punctures.

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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