Our results show that epicardial-level of I(to) acts as a negative, rather than positive regulator of myocyte mechanical properties in canine ventricular myocytes.
Abnormal Ca 2þ signals, including delayed/desynchronized onset of Ca 2þ transients, occasional missing Ca 2þ transients and Ca 2þ transient alternans, are often observed in cardiac muscles under pathophysiological conditions. To investigate how these abnormal Ca 2þ responses can be generated, we monitored membrane potential and Ca 2þ signals using a fluorescent membrane potential indicator and a Ca 2þ indicator in the same preparation. Papillary muscles were dissected from guinea pig ventricles and loaded with di-4-ANEPPS and rhod-2 AM. Mono-wavelength Ca 2þ signals and ratiometric action potential signals were sequentially obtained using the Nipkow-disc confocal microscope and W-view system. Control signals were obtained from cardiac muscles paced in a normal Krebs solution, whereas abnormal Ca 2þ signals were induced by pacing them in a non-flowing Krebs solution. There were two types of causes for the failed and alternating Ca 2þ transient generation, i.e., failed or alternating immature action potential generation and abnormal EC coupling with relatively constant action potentials. In cells showing delayed initiation of Ca 2þ transients, action potential onset was also delayed and the rate of rise was slower than that in healthy cells. Effects of an inhibitor of gap junction channels and a Na þ channel blocker suggest that the delayed onset of action potentials can be explained primarily by impaired gap junctions and partly by Na þ channel inactivation.
Background
To evaluate the effect of stent boost subtract (SBS) imaging on stent underexpansion during percutaneous coronary intervention (PCI) in patients with acute ST-segment elevation myocardial infarction (STEMI) by optical coherence tomography (OCT).
Methods
One hundred thirty-eight STEMI patients who underwent drug-eluting stent (DES) implantation were prospectively recruited and divided into the SBS group (69 cases) and the CAG group (69 cases) according to whether SBS was used to guide PCI. Finally, OCT was performed on all enrolled patients, and the OCT results were used as the gold standard to evaluate the impact of standard SBS technology on stent underexpansion immediately after DES implantation.
Results
SBS identified 51 patients (24%) with stent underexpansion while OCT identified 56 patients (27.2%). SBS has a sensitivity of 80%, a specificity of 96%, a positive predictive value of 88%, and a negative predictive value of 93% for identifying stent underexpansion.
Conclusion
Compared with OCT, SBS technology is a rapid stent imaging evaluation method that can accurately quantify the stent expansion level and is time-saving and economical.
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