Masataka Mitsuno

Simultaneous epicardial and endocardial activation sequence mapping in the isolated canine right atrium.

BackgroundSince the atria are thin-walled structures, most studies that have examined the spread of activation in the atria have assumed that they behave electrophysiologically as a two-dimensional surface. It was the objective of this study to determine whether or not this assumption is true by simultaneously mapping the epicardial and endocardial activation sequences in the right atrium. Methods and ResultsIdentical precisely superpositioned epicardial and endocardial electrode templates with 250 unipolar electrodes each were used to map the isolated canine right atrium (N=8) during continuous perfusion and superfusion with Krebs-Henseleit buffer. Data were recorded during control conditions (normal sinus rhythm), continuous pacing (S1S1=300 msec), and premature stimulation (S1S2=effective refractory period+5 msec). Pacing was performed at two sites, one located on the inferior crista terminalis and one lateral to the crista terminalis on a pectinate muscle. Tachyarrhythmias were induced by a single extrastimulus during the continuous perfusion of acetylcholine (10–3S mol/L). Individual electrode sites were correlated with the gross anatomy and histology. Activation time differences were calculated between each two corresponding epicardial and endocardial sites. There were differences in the activation times between the epicardium and endocardium during all experimental conditions. However, the average difference for each condition was <1 msec, suggesting that overall activation did not spread faster on either the epicardium or the endocardium, even though in certain regions one surface could lead the other. The dispersion of time differences was smallest during normal sinus rhythm and continuous pacing (SD=5.6-5.8 msec) and largest after premature stimulation (SD=6.3 msec for crista pacing, <P 0.05; SD=8.1 msec for pacing lateral to the crista, p<0.001). Differences in the activation sequence correlated with the underlying anatomic architecture. The largest differences in activation times between the epicardium and endocardium were associated with those regions of the atrium where pectinate muscles ran below the epicardial surface. The pectinate muscles in those areas were often discontinuous with the epicardial surface and facilitated the discordant epicardial-endocardial activation. The discordant activation was also found in regions where the atrial wall thickness was <0.5 mm and correlated with transmural differences in fiber orientation. A tachyarrhythmia induced in the presence of acetylcholine, which demonstrated a focal activation pattern, was shown to have a reentrant loop that used free-running muscle bundles connecting the epicardial and endocardial surfaces, resulting in a three-dimensional pathway. ConclusionsThe findings of this study demonstrate that epicardial and endocardial activation can be discordant in specific regions and that discordance increases with abnormal activation sequences. Many of the differences in the epicardial and endocardial activation can be correlated with the heterogeneity of the anatomic architecture of the right atrium. The study also demonstrates that reentry can occur in a three-dimensional plane using the epicardial and endocardial surfaces connected by transmural muscle fibers.

Beneficial effects of mini-cardiopulmonary bypass on hemostasis in coronary artery bypass grafting: analysis of inflammatory response and hemodilution.

We compared the inflammatory response, hemodilution, and blood loss in patients who underwent mini-cardiopulmonary bypass (CPB) or conventional CPB during coronary artery bypass grafting (CABG). Ninety-eight consecutive patients with ischemic heart disease were randomly assigned to mini-CPB (n = 34) or conventional CPB (n = 64). Interleukin (IL) −8 and neutrophil elastase levels were measured before and after surgery. Hemodilution during CPB, blood loss during and after surgery were also evaluated. Compared with the conventional group, the mini-CPB group had lower levels of IL-8 on postoperative day 1 (8.3 ± 6.4 vs. 19 ± 11 pg/mL, p = 0.016) and of neutrophil elastase on postoperative days 1 (127 ± 52 vs. 240 ± 100 &mgr;g/L, p = 0.013) and 2 (107 ± 17 vs. 170 ± 45 &mgr;/L, p = 0.0001). The mini-CPB group also has less blood loss during (620 ± 595 vs. 978 ± 658 mL, p = 0.012) and after the operation (578 ± 310 vs. 1,002 ± 651 mL, p = 0.0034) and a hemodilution ratio of 14 ± 2 vs. 25% ± 3%, p < 0.0001. Thus, mini-CPB attenuated the inflammatory response and hemodilution, resulting in blood conservation in patients undergoing CABG.

Return Cycle Mapping After Entrainment of Ventricular Tachycardia

BACKGROUNDnThe central common pathway, which is the target for ablation in reentrant ventricular tachycardia, can be localized by entrainment mapping techniques. However, localization of the pathway is not always possible because of the elevated pacing threshold and the low voltage and fractionated potentials at the pathway. We examined whether return cycle mapping after entrainment localizes the pathway without pacing at the pathway or recording the potentials from the pathway and determined the required electrode resolution to localize the pathway.nnnMETHODS AND RESULTSnEpicardial mapping was performed with 253 unipolar electrodes during and after entrainment of 13 morphologies of ventricular tachycardia that were induced in dogs 4 days after infarction. The return cycle was calculated by subtracting the first activation time from the second activation time after the last stimulus and the return cycle distribution map was constructed for each stimulation site. The return cycle isochrones equal to the ventricular tachycardia cycle length converged on the lines of conduction block irrespective of the stimulation site, and the central common pathway was localized at the region between the intersections of the return cycle isochrones after entrainment from different stimulation sites. The potentials from the central common pathway were not required to localize the pathway, and the mapping accuracy did not change with or without analysis of the potentials from the pathway. According to the correlation between the electrode resolution and the mapping accuracy, an interelectrode distance of 8.5 mm was estimated as sufficient resolution for successful tachycardia termination during radiofrequency ablation guided by return cycle mapping.nnnCONCLUSIONSnReturn cycle mapping after entrainment localizes the central common pathway without pacing at the pathway or recording the potentials from the pathway. This new mapping technique could improve the success rate of the ablative procedures.

Changes in left anterior descending coronary artery flow profiles after coronary artery bypass grafting examined by means of transthoracic Doppler echocardiography

OBJECTIVEnWe sought to investigate the changes of velocity profiles in the left anterior descending coronary artery after coronary artery bypass grafting using transthoracic Doppler echocardiography.nnnMETHODSnForty-five patients who received a bypass graft to the left anterior descending coronary artery were studied. Before coronary artery bypass grafting, Doppler velocity profiles of the distal left anterior descending coronary artery were recorded with transthoracic Doppler echocardiography. Peak systolic velocity, mean systolic velocity, peak diastolic velocity, mean diastolic velocity, total velocity time integral, systolic velocity time integral, and diastolic velocity time integral were measured. Three weeks after coronary artery bypass grafting, left anterior descending coronary artery antegrade flow in the distal portion of the anastomosis was obtained by using the same method. Coronary angiography was performed before and 3 weeks after coronary artery bypass grafting.nnnRESULTSnThe overall success rate of measuring the left anterior descending coronary artery flow was 60.0% preoperatively and 80.0% postoperatively. In 25 patients, in whom all parameters were obtained both before and after coronary artery bypass grafting, the following increased significantly after coronary artery bypass grafting: peak systolic velocity (14.86 +/- 7.50 vs 25.07 +/- 17.02 cm/s, P =.0045), mean systolic velocity (9.86 +/- 5.42 vs 18.03 +/- 12.94 cm/s, P =.0026), peak diastolic velocity (24.26 +/- 12.54 vs 48.28 +/- 31.66 cm/s, P =.0021), mean diastolic velocity (14.94 +/- 6.65 vs 30.36 +/- 20.71 cm/s, P =.0022), diastolic velocity time integral (7.22 +/- 2.88 vs 15.55 +/- 10.39 cm, P =.0009), total velocity time integral (10.50 +/- 4.48 vs 19.27 +/- 12.63 cm, P =.0034), and diastolic-to-systolic velocity time integral ratio (3.09 +/- 1.53 vs 4.97 +/- 2.75, P =.0044). Angiography showed graft patency and no significant change in left anterior descending coronary artery stenosis in all patients.nnnCONCLUSIONSnTransthoracic Doppler echocardiography showed a significant increase in some parameters in left anterior descending coronary artery flow after coronary artery bypass grafting. Measurement of left anterior descending coronary artery flow by means of transthoracic Doppler echocardiography might be a noninvasive method to evaluate the effect of bypass grafting on the left anterior descending coronary artery.

VALVE REPAIR FOR MITRAL REGURGITATION ASSOCIATED WITH ISOLATED DOUBLE-ORIFICE MITRAL VALVE

Double-orifice mitral valve (DOMV) can occur as an isolated lesion or in association with other cardiac malformations of which atrioventricular canal defect is most common. 1 Isolated DOMV is, however, rarely identified when the valve is functioning normally. We present here a case with mitral regurgitation in isolated DOMV in which valve repair was done successfully. A 55-year-old man was referred to our hospital with exertional dyspnea. Physical examination showed a grade 4/6 holosystolic murmur at the left fourth intercostal space. The electrocardiogram showed atrial fibrillation. The chest x-ray film showed a dilated left atrium. Transthoracic two-dimensional and color Doppler echocardiography showed a DOMV with grade 4 mitral regurgitation because of a torn chorda at the mitral orifice of the anterolateral side. The left ventricular diastolic and systolic dimensions by echocardiography were 74 mm and 42 ram, respectively. Cardiac catheterization revealed a peak pulmonary capillary wedge pressure of 21 mm Hg. The left ventriculogram showed severe mitral regurgitation. An operation was done with the use of standard cardiopulmonary bypass with moderate hypothermia (28 ° C) and cold cardioplegic arrest. The left atrium was entered through the standard longitudinal incision. The mitral valve was found to have two orifices, which were completely separated by a fibromuscular bridging tissue (Fig. 1). The orifices were almost equal in size: the posteromedial orifice was 30 ram; the anterolateral orifice, 25 mm. Each orifice had its own site of chordal insertion. No cleft was identified on either the anterior or posterior leaflet of each orifice. One half of the posterior leaflet of the anterolateral orifice was found to have prolapse because of a torn chorda. A quadrangular segmental resection of the prolapsed posterior leaflet was done. Large, pledgeted 2-0 sutures were placed at the level of the anulus for plication. The split leaflet was sutured with interrupted 4-0 polypropylene sutures. Because the fibromuscular bridging tissue seemed to be unsuitable for placement of the annuloplasty ring, another pledgeted suture was added to reinforce the plicated anulus. By this procedure, the anterolateral orifice was reduced to 10 mm in diameter. Transesophageal Doppler echocardiography showed trivial mitral regurgitation from the repaired anterolateral orifice. The patient was discharged from the hospital on postoperative day 15 after an uneventful recovery. Various classifications for DOMV have been proposed on the basis of the size and location of the two orifices. 1-3 The case presented here is an example of a complete type in the classification of Trowitzsch and colleagues 2 and of a central type in the classification of Cascos, Rabago, and Sokolowski. 3 In the majority of isolated cases of DOMV, the second orifice is found as an accessory orifice, which is the cause of mitral regurgitation, s4 For this type of accessory orifice, simple closure has been the choice to correct mitral regurgitation. 4 Mitral regurgitation associated with isolated DOMV with two equal orifices as in our case has rarely been described in previous literature. 5 Because no cleft was identified at operation, the choices of treatment seemed to be repair or closure of the valve. In a case with two equal orifices, however, closure of one orifice might produce acute diminution of the mitral valve area leading to a stenotic condition. 6 In addition, closure of the orifice might possibly cause deformity at the fibrous bridging tissue, leading to incompetence of another intact orifice. Considering the possible problem in closure of the orifice and the finding of a torn chorda located only at the posterior leaflet, valve repair was chosen in our case. The

Evaluation of closed cardiopulmonary bypass circuit for aortic valve replacement.

Since 2005, we have used a novel technique based on the closed cardiopulmonary bypass system without cardiotomy suction (minimal cardiopulmonary bypass [mini-CPB]) for aortic valve replacement (AVR). In this study, we investigated the clinical advantages of this approach. We prospectively studied 32 patients who underwent isolated AVR using the mini-CPB (group M, n = 13) or conventional CPB (group C, n = 19). We compared the hemodilution ratio, serum interleukin (IL)-6 and IL-8 levels, and blood transfusion volume between the two groups. The characteristics, duration of CPB, and aortic cross-clamping time did not differ between the two groups. The hemodilution ratio was significantly lower in group M just after starting CPB (M vs. C: 14% ± 2% vs. 25% ± 3%, p = 0.0009). IL-6 levels increased significantly after surgery in both groups, but the postoperative levels were significantly lower in group M at 6 (84.9 ± 24.9 pg/ml vs. 152 ± 78 pg/ml, p = 0.042) and 12 (72.7 ± 36.1 pg/ml vs. 123 ± 49.6 pg/ml, p = 0.029) hours after CPB. There were no differences in IL-8 or blood transfusion volume after CPB. Mini-CPB offers an alternative to conventional CPB for AVR and has some advantages regarding hemodilution and serum IL-6 levels. However, it is unlikely to become the standard approach for AVR because there are no marked clinical advantages of mini-CPB.

Improved Management of Selective Cerebral Perfusion in Aortic Arch Surgery

To establish a safe and reliable method for cerebral protection in aortic arch surgery, the authors attempted antegrade selective cerebral perfusion (SCP) based on the characteristics of jugular venous oxygen saturation (SjO2). Twenty patients were divided into two groups: a control group and SCP group. In the control group, in 13 adult patients undergoing cardiac surgery using standard hypothermic cardiopulmonary bypass, the relationship between SjO2 and nasopharyngeal temperature (NPT) during rewarming showed an inverse linear correlation:SjO2 = -2.3 NPT + 133 (r = 0.616). In the SCP group, seven patients with aortic arch aneurysm underwent surgery using SCP performed through direct cannulation of the innominate and left carotid arteries. While on SCP (83 +/- 24 min), the blood was warmed from 28 to 36 degrees C. Cerebral perfusion pressure of 40-60 mm Hg was necessary to maintain the SjO2 equal to the value in the control group at each NPT during SCP in all seven patients. None of the patients had any post operative complications. Our experience suggests that SCP can be safely performed at both mild hypothermia and normothermia under monitoring of perfusion pressure and SjO2 in aortic arch surgery.

Pretreatment with the Free Radical Scavenger Edaravone Mitigates Kidney Glycogen Depletion and Neutrophil Infiltration after Leg Ischemia in a Rat Model: A Pilot Study

Objective: We have previously shown that pretreatment with the free radical scavenger edaravone (Radicut®, Mitsubishi Tanabe Pharma Co., Japan) mitigated skeletal muscle damage due to ischemia reperfusion. In this study, we sought to validate its use in an experimental model of myonephropathic-metabolic syndrome (MNMS). Methods: Either edaravone (3.0u2009mg/kg; edaravone group; n=4) or saline (saline group; n=6) was intraperitoneally injected into male Lewis rats (508±31u2009g). Normal kidneys were harvested as control (n=3). MNMS was induced by bilaterally clamping the common femoral arteries for 5u2009h and declamping 5u2009h later. Kidney damage was evaluated by quantifying Periodic Acid Schiff (PAS)-positive area (glycogen storage) and esterase-positive cells (neutrophil infiltration). Results: The PAS-positive area in the saline group was significantly lower than that in the normal group (36.9±2.6 vs. 66.9±1.2%, P<0.01); the PAS-positive area in the edaravone group remained comparable to that in the normal group (52.9±0.9%, P<0.01). Esterase-positive cells in the saline group were significantly higher than in normal kidneys (62.4±5.6 vs. 17.5±2.4 cells/mm2, P<0.01), while they were significantly reduced in the edaravone group (32.8±5.7u2009cells/mm2, P<0.01). Conclusion: Edaravone pretreatment mitigates MNMS-induced kidney damage by reducing both glycogen depletion and neutrophil infiltration.

Life-threatening Migration of ALN Inferior Vena Cava Filter to Right Ventricle

A 40-year-old man underwent emergent pulmonary artery thromboembolectomy for pulmonary artery thromboembolism, and an ALN filter was placed in the inferior vena cava immediately after the operation. He had sudden ventricular tachycardia with dyspnea on postoperative day 6. An emergent operation was successfully performed, and the ALN filter was observed at the tricuspid valve with a large amount of the thrombus. Migration of the inferior vena cava filter to the right ventricle is a life-threatening complication that may result from residual deep vein thrombosis.