Tomoaki Saeki

Relationship between blood pressure obtained from the upper arm with a cuff-type sphygmomanometer and central blood pressure measured with a catheter-tipped micromanometer

Recently, the importance of central blood pressure for cardiovascular risk stratification has been emphasized. Accordingly, the differences in peak systolic and bottom diastolic pressures between the ascending aorta and the brachial artery should be clarified. Study subjects consisted of 82 consecutive patients with suspected coronary artery disease who underwent cardiac catheterization, and in whom ascending aortic pressure waveform was obtained using a catheter-tipped micromanometer, and at the same time systolic and diastolic pressures were measured (single measurement) from the right upper arm with a cuff-type sphygmomanometer based on the oscillometric technique. No significant systematic difference (bias) was found between the peak pressure obtained in the ascending aorta and the systolic pressure from the right upper arm (133.6 ± 25.1 vs 131.8 ± 21.5 mmHg, not significant). Bland–Altman analysis showed only a small bias of +1.8 mmHg, and the limits of agreement were 25.4 mmHg and −21.8 mmHg. In contrast, the bottom pressure in the ascending aorta was significantly lower compared with the diastolic pressure from the upper arm (68.5 ± 10.7 vs 73.0 ± 12.4 mmHg, P < 0.0001). Bland–Altman analysis showed a small but significant bias of −4.5 mmHg, and the limits of agreement were 14.1 mmHg and −23.1 mmHg. The observed biases seemed to remain within practical range. However, random variation in the two measurements was rather large. This is considered to be caused by the random error in the single measurement with the cuff-type sphygmomanometer.

Electrophysiological demonstration and activation of μ-opioid receptors in the rabbit sinoatrial node

Summary: To investigate the presence of opioid receptors and their physiological role in cardiac pacemaker cells, we studied electrophysiological effects of fentanyl citrate, an activator of the μ-opioid receptors, on the spontaneous action potential (AP) and membrane currents, using small preparations (0.2 χ 0.2 χ 0.1 mm) of rabbit sinoatrial (SA) node (SAN). Fentanyl (0.1–3 μAM) progressively decreased the AP amplitude (APA), maximal rate of depolarization (MRD), and spontaneous firing frequency (SFF) and prolonged the AP duration (APD) and diastolic interval in a concentration-dependent manner. At 1 μM, the spontaneous activity ceased in two of the eight preparations. These actions were blocked by a μ-opioid receptor antagonist, β-funaltrexamine (p-FNA), but were not modified by either β-opioid receptor antagonist nor-binaltorphimine (nor-BNI), or β-opioid receptor antagonist ICI-174864. In voltage-clamp experiments using double microelectrode techniques, 1 μM fentanyl reduced the Ca2+ current (ICa) obtained on step depolarization from −40 to 0 mV by 19.9 ± 9.3% (p < 0.05, n = 5), the fast and slow components of the delayed rectifying K+ current (IKfast, IKslow) tail obtained on repolarization from 10 to –60 mV by 54.7 ± 4.7 and 41.4 ± 2.4% (p < 0.05, n = 4), and the hyperpolarization-activated inward current at −90 mV by 12.6 ± 0.5% (p < 0.05, n = 7), respectively. The gating kinetics of ICa and IKslow were not altered. However, the steady-state activation curve for IKfast was shifted toward more negative potentials by 6.9 ±1.1 mV and the deactivation time constant of IKfast was prolonged from 92 ± 8 to 114 ± 4 ms by 1 μM fentanyl (p < 0.05, n = 4). These results suggest (a) that μ-opioid receptors are abundantly present in rabbit SAN cells and (b) that activation of these receptors by endogenous and exogenous opioids exerts a negative chronotropic action by decreasing the conductance of all the membrane currents and prolonging the deactivation time constant of IKfast in rabbit SAN cells.

Resolution of Left Ventricular Thrombus Secondary to Tachycardia-Induced Heart Failure with Rivaroxaban

A 42-year-old man was admitted to our hospital because of lumbago and tachycardia-induced heart failure. Transthoracic echocardiography revealed impaired left ventricular function and a ball mass of thrombus in the left ventricle (LV). He was found to have systemic embolism in the spleen, kidneys, brain, and limbs. The patient was treated with limb thrombectomy followed by anticoagulation. Seven days after the direct factor Xa inhibitor, rivaroxaban, was initiated, transthoracic echocardiography was repeated, revealing disappearance of the LV thrombus without any clinical signs of cardiogenic embolism. His heart failure responded well and the LV wall motion had improved. This case suggests rivaroxaban has fibrinolytic effects on thrombi even in the LV.

Selective block of delayed rectifying potassium current in the rabbit sinoatrial node by a novel class III antiarrhythmic agent MS-551

SummaryElectrophysiological actions of MS-551, a novel class III antiarrhythmic agent, were studied using small preparations (0.2 × 0.2 × 0.1mm) of the rabbit sinoatrial (SA) node. MS-551 (0.1–3 µM) exerted a negative chronotropic action by prolonging the action potential duration and diastolic interval. Automaticity was completely suppressed in 5 of 6 preparations at 1–3 µM. Voltage clamp experiments using double microelectrode techniques revealed that MS-551 (0.1–10µM) blocked the delayed rectifying K+ current (IK) in a concentration-dependent manner, and the block was almost saturated at >1 µM, attaining 60% ± 10% at 10 µM (n = 5). The MS-551-sensitive IK tail (Kd = 0.4µM, Hill r = 1.4,n = 5) had fast and slow components of deactivation. MS-551 (1 µM) reduced the amplitudes of control IK fast and IK slow from 20 ± 4 and 11 ± 4 nA to 8 ± 3 and 5 ± 3 nA, respectively (P < 0.01,n = 4). Although the fast deactivation time constant at −60mV remained unaltered (127 ± 12 vs 113 ± 13ms), the slow deactivation time constant was prolonged from 1,117 ± 130 to 1,555 ± 407ms by 1µM MS-551 (P < 0.05). This agent shifted the steady-state activation curve for IK from −21 ± 2 to −26 ± 4mV and increased the slope factor from 8 ± 1 to 9 ± 1mV (P < 0.05,n = 4). The fully-activated IK exhibited prominent inward rectification and was reduced by MS-551. These results suggest that (1) MS-551 prolongs the action potential duration and diastolic interval, and exerts a negative chronotropic action by blocking IK, (2) MS-551 has a higher affinity for the activated than the resting state K+ channel, and (3) this agent may either preferentially block one type of IK, or stabilize a single population of IK in a subconductance state in the rabbit SA node.

Review of High-intensity Interval Training in Cardiac Rehabilitation.

For the secondary prevention of cardiovascular disease, comprehensive cardiac rehabilitation is required. This involves optimal medical therapy, education on nutrition and exercise therapy, and smoking cessation. Of these, efficient exercise therapy is a key factor. A highly effective training protocol is therefore warranted, which requires a high rate of compliance. Although moderate-intensity continuous training has been the main training regimen recommended in cardiac rehabilitation guidelines, high-intensity interval training has been reported to be more effective in the clinical and experimental setting from the standpoint of peak oxygen uptake and central and peripheral adaptations. In this review, we illustrate the scientific evidence for high-intensity interval training. We then verify this evidence and discuss its significance and the remaining issues.

Ruptured Sinus of a Valsalva Aneurysm Associated with Autosomal-Dominant Polycystic Kidney Disease in an Elderly Patient : Report of a Case

We report herein the case of a 71-year-old woman with autosomal-dominant polycystic kidney disease (ADPKD), who was referred to our hospital for investigation of facial edema. Echocardiography demonstrated a large aneurysm arising from the non-coronary sinus of Valsalva, with a left to right shunt and jets of blood passing from the aneurysm toward the septal leaflet of the tricuspid valve. Surgical treatment was successfully carried out by resecting the aneurysmal wall and performing a patch closure of the orifice. It is well known that ADPKD predisposes patients to cardiovascular disease, and this case report serves to demonstrate that when a patient with ADPKD presents with progressive heart failure, the possibility of a ruptured sinus of a Valsalva aneurysm must be considered.

Effects of membrane lipid peroxidation by tert butyl hydroperoxide on the sodium current in isolated feline ventricular myocytes

SummaryMembrane lipid peroxidation is known to play a pivotal role in the genesis of coronary reperfusion arrhythmias in both experimental and clinical settings. To elucidate the electrophysiological mechanisms underlying these arrhythmias, the effects of tert butyl hydroperoxide (TBH) on the Na+ current (INa) in isolated feline ventricular myocytes were studied using whole-cell patch clamp techniques under 100% O2 bubbling. This agent at 20 mM inhibited INa from 2.2 ± 1.3 to 1.7 ± 1.0nA (P < 0.01,n = 7) without changing time courses of INa inactivation. Twenty millimoles TBH shifted the steady-state inactivation curve for INa from −77.4 ± 1.7 to −81.3 ± 1.8mV when measured at INa half inhibition voltage (P < 0.01,n = 7), but did not affect the slope factor. The kinetics of INa recovery from inactivation remained unchanged. These findings suggest that lipid peroxidation in the membrane by TBH reduces INa conductance and voltage-dependent INa availability, most likely as a result of structural damage to the Na+ channels.

Early detection of twiddler syndrome due a congestion alert by remote monitoring

There are often false‐positive alerts of thoracic impedance monitoring; however, the “false‐positive alerts” might indicate any clinical problem of patient. In the present case, an alert for a drop in intrathoracic impedance, which generally indicates exacerbation of heart failure, enabled early detection of twiddler syndrome.