Toshiaki Akita

Cerebrospinal Dysfunction After Endovascular Stent-Grafting via a Median Sternotomy: The Frozen Elephant Trunk Procedure

BACKGROUND Endovascular stent grafting through a median sternotomy for a distal arch aneurysm (the frozen elephant trunk procedure) is an alternative to synthetic graft replacement. But spinal cord dysfunction can easily occur as a complication after surgery. Although its cause is uncertain, some attempts at prevention have been instituted. We address the mechanism of spinal cord dysfunction and evaluate the efficacy of our preventive measures. METHODS There were 22 men and 2 women with an average age of 71 (59 to 83) years. There were 22 true aneurysms (13 fusiform, nine saccular), one chronic dissection, and one penetrating aortic ulcer. The following strategies for prevention of spinal cord dysfunction were utilized: low flow perfusion through both axillary arteries (n = 10); pigtail catheter guidance (n = 19); use of a shorter graft with anchoring sutures (n = 12); flooding of the operative field with carbon dioxide (n = 7); aortic unclamping (n = 7), and use of ultra-thin woven Dacron grafts (n = 15). RESULTS There was no operative mortality, but cerebrospinal dysfunction complicated four cases (17%): one paraplegia, one stroke along the basilar artery, and two cases of temporary spinal cord dysfunction (paresthesia of the right leg and urinary disturbance). Cerebrospinal dysfunction tended to occur in fusiform aneurysms (31%, p = 0.044). Except when low flow antegrade perfusion through both the axillary arteries was utilized, which resulted in no cases of paraplegia or paraparesis (p = 0.064), the methods used for prevention of cerebrospinal dysfunction appeared to have little efficacy. CONCLUSIONS Cerebrospinal dysfunction is a serious complication of the frozen elephant trunk procedure. Its cause has not been clarified, but it tends to occur in fusiform-type aneurysms. Antegrade perfusion through both axillary arteries while the aorta is open may be helpful in its prevention.

Repetitive atrial flutter as a complication of the left-sided simple maze procedure

BACKGROUND Of 41 patients who had undergone a left-sided simple maze procedure, 4 (9.8%) developed repetitive tachycardia due to atrial flutter, and required radiofrequency catheter ablation. Linear ablation of the right atrial isthmus was effective to treat atrial flutter. METHODS We conducted an electrophysiologic study of atrial flutter and determined its reentry circuit on the atrium. We consider how to reduce atrial flutter after the left-sided simple maze procedure. RESULTS Common atrial flutter through the right atrial isthmus was induced in all 4 patients, and linear ablation on the right atrial isthmus was effective in 3 of these. An incisional atrial flutter around the right atriotomy was also induced in 2 of 4 patients; both were successfully treated by linear ablation between the right atriotomy and the inferior vena cava. CONCLUSIONS Common atrial flutter through the right atrial isthmus is a risk after the left-sided simple maze procedure. When a left-sided simple maze procedure is performed, sufficient cryoablation on the right atrial isthmus of the arrested heart should be administered to prevent postoperative atrial flutter.

Midkine prevents ventricular remodeling and improves long-term survival after myocardial infarction

Cardiac remodeling is thought to be the major cause of chronic heart dysfunction after myocardial infarction (MI). However, molecules involved in this process have not been thoroughly elucidated. In this study we investigated the long-term effects of the growth factor midkine (MK) in cardiac remodeling after MI. MI was produced by ligation of the left coronary artery. MK expression was progressively increased after MI in wild-type mice, and MK-deficient mice showed a higher mortality. Exogenous MK improved survival and ameliorated left ventricular dysfunction and fibrosis not only of MK-deficient mice but also of wild-type mice. Angiogenesis in the peri-infarct zone was also enhanced. These in vivo changes induced by exogenous MK were associated with the activation of phosphatidylinositol 3-kinase (PI3K)/Akt and MAPKs (ERK, p38) and the expression of syndecans in the left ventricular tissue. In vitro experiments using human umbilical vein endothelial cells confirmed the potent angiogenic action of MK via the PI3K/Akt pathway. These results suggest that MK prevents the cardiac remodeling after MI and improves the survival most likely through an enhancement of angiogenesis. MK application could be a new therapeutic strategy for the treatment of ischemic heart failure.

Deferoxamine, an iron chelator, reduces myocardial injury and free radical generation in isolated neonatal rabbit hearts subjected to global ischaemia-reperfusion.

The protective action of deferoxamine, an iron chelator, against functional and metabolic deteriorations of ventricular muscle, induced by ischaemia-reperfusion, was investigated in Langendorff-perfused hearts of neonatal rabbits in comparison with superoxide dismutase (SOD) plus catalase. The perfused hearts were subjected to normothermic (37 degrees C) global ischaemia for 45 min following cardiac arrest with St Thomas cardioplegic solution and then reperfused with oxygenated Krebs-Henseleit solution. In control hearts, the recovery of the left ventricular developed pressure (LVDP) after 30 min reperfusion was 50.7 +/- 3.1% (mean +/- SE, n = 5) of the pre-ischaemic value. The LVDP recovery was significantly improved in the hearts treated with deferoxamine at 10-100 microM (89.4 +/- 1.4% at 30 microM, P < 0.01 vs. control). The improvement in LVDP was less prominent when treated with 30 x 10(4) U/l SOD plus 30 x 10(4) U/l catalase (67.9 +/- 2.0%, P < 0.01 vs. deferoxamine at 30 microM). CPK leakage into the coronary effluent during the initial 5 min of reperfusion was reduced to around half of the control value with 30 microM deferoxamine (P < 0.05 vs. control), while unaffected by the addition of SOD plus catalase. Free radicals in the coronary effluent were measured with electron spin resonance spectroscopy in separate experiments by using a spin-trapping agent, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). A burst of DMPO-OH signal was detected during the initial minutes of reperfusion. The intensity of DMPO-OH signal was significantly reduced by 30 microM deferoxamine to about one-third of control.(ABSTRACT TRUNCATED AT 250 WORDS)

Midterm results for endovascular stent grafts via median sternotomy for distal aortic arch aneurysm

Dislocation or perigraft leakage is a major problem during the follow-up period for endovascular stent graft (EVG) implantation via median sternotomy for distal aortic arch aneurysm. Anchoring sutures have been applied for the prevention of these complications. Here, we evaluate the midterm results and the efficacy of anchoring sutures. There were 21 male and 2 female patients enrolled in the study with an average age of 70 years (59–83). Aneurysm types were 21 true aneurysms (13 fusiform, 8 saccular), 1 chronic dissection, and 1 penetrating aortic ulcer. Total arch replacement was performed in two patients and aortocoronary bypass grafting was combined in four patients. Anchoring sutures to fix the EVG via median sternotomy were applied for 11 recent patients. The average follow-up period was 44 (22–79) months. There were no operative mortalities, but one case of paraplegia, one of stroke, and two of temporary spinal cord dysfunction. Complications related to EVG via median sternotomy occurred in five patients who had not received anchoring sutures, but the 11 patients with anchoring sutures showed no EVG-related complications. A chronic type B dissection revealed impending rupture due to false lumen infection 1 year after operation and repeat surgery was performed. Stent dislocation occurred in four patients, two of whom required repeat surgery via left thoracotomy due to endoleakage 3 and 4 years after surgery. One died from aneurismal rupture 5 years after surgery. One required emergency graft replacement because of graft perforation 5 years after surgery. The proportion of patients free from EVG-related events at 5 years after surgery was 75%. Anchoring sutures (P = 0.0155) and a large aneurysm of more than 80 mm (P = 0.0190) were predictors of late EVG-related complications. There were five late deaths: two were from stroke, one from rupture, one from cancer, and one from multiple organ failure after repeat surgery. EVG shortens postoperative recovery with relatively lower mortality, but spinal cord injury is a complication occurring with a relatively high rate. Patients with large aneurysms are not good candidates for EVG implantation via median sternotomy Anchoring sutures to fix the EVG to the aortic wall should help prevent EVG-related events and improve the durability of EVG.

Late mortality and morbidity in elderly patients with mechanical heart valves.

A retrospective study was performed in patients under and over 65 years old implanted with a mechanical valve, to compare late mortality and morbidity. Of 381 patients who underwent mechanical valve replacement at Nagoya University in the 1990s, 357 (11 hospital deaths and 13 lost to follow-up; 96.4% follow-up rate) were followed up for 7.9 ± 3.3 years (2,811 patient-years). They were divided into two groups either side of 65 years of age at operation. The young and elderly patient groups contained 275 and 82 patients, respectively. The survival rate in the young group was 96.1% (95% confidence interval, 93.7%–98.5%) at 5 years and 92.0% (95% confidence interval, 88.3%–95.7%) at 10 years, which was significantly better than 88.0% (95% confidence interval, 80.6%–95.4%) at 5 years and 73.8% (95% confidence interval, 66.2%–85.4%) at 10 years in the elderly group. The two groups did not differ significantly in the incidence of thromboembolic events, bleeding events, endocarditis, or reoperation. We are also encouraged by the fact that mechanical valves are not a risk factor for late mortality or morbidity, even in elderly patients.

Entry Closure and Aortic Tailoring for Chronic Type B Aortic Dissection

Although graft replacement for chronic type B dissection is the standard operation, this operation is invasive to some extent, and the mortality and morbidity remain high. We describe a simple and less invasive technique using initial entry closure and aortic tailoring of the dissected lumen.

Incomplete transmural ablation caused by bipolar radiofrequency ablation devices

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A pilot randomized study of the neutrophil elastase inhibitor, Sivelestat, in patients undergoing cardiac surgery.

The primary objective of this study was to determine the feasibility and safety of treatment with Sivelestat in humans to attenuate post-cardiopulmonary bypass lung injury. Twenty patients scheduled to undergo on-pump coronary artery bypass surgery were randomized to receive either 0.3 mg/kg/h intravenous Sivelestat sodium (Sivelestat group; n=10) or isotonic sodium chloride solution (placebo group, n=10), peri-operatively. Postoperative adverse events were recorded until hospital discharge. The alveolar-arterial oxygen gradient (A-aDO(2)), intrapulmonary shunt (Qs/Qt) and dynamic lung compliance were determined four times peri-operatively as secondary exploratory outcomes. All patients completed study protocol without discontinuation of intervention. The number of total adverse clinical outcomes, including atrial fibrillation and superficial wound infection, was nine in seven patients in the placebo group and four in four patients in the Sivelestat group (P=0.37). The mean duration of the postoperative hospital stay was shorter in the Sivelestat group (19.0+/-3.4 vs. 25.6+/-9.1, P=0.04). The exploratory analysis of relative changes in lung functions showed trends toward attenuation of lung injury in the Sivelestat group in all three pulmonary parameters, though the inter-group difference could be due to chance (P>0.05). It is feasible to administer Sivelestat as a preventive measure against lung dysfunction after cardiopulmonary bypass.

Deferoxamine reduces the reperfusion injury in isolated neonatal rabbit hearts after hypothermic preservation

The protective action of deferoxamine, an iron chelator, against reperfusion injury following hypothermic preservation was investigated in the Langendorff-perfused hearts of neonatal rabbits. Left ventricular function and radical generation were used as parameters to evaluate functional and metabolic changes. The free radicals in coronary effluents were measured with an electron spin resonance spectroscope using a spin trapping agent, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The hearts were preserved in cold St. Thomas solution at 4°C for 6 h following cardiac arrest, then reperfused with oxygenated Krebs-Henseleit solution in a control. Deferoxamine (100 μM) was added to the perfusate just prior to reperfusion in group I, and 3 min after the start of reperfusion in group II. In the control group, the left ventricular developed pressure (LVDP) after 30-min reperfusion recovered up to 43.5±3.1% (mean ± SD, n=5) the preischemic value. Group I showed a significant improvement in LVDP recovery after 30-min reperfusion at 57.1±3.1% (P<0.01 vs control), but group II did not (47.5±2.3%). When a burst of DMPO-OH signals was detected during the initial 5 min of reperfusion, the signal intensity in group I was significantly reduced to about 35–40% of the control value. Group II showed a similar intensity to the control group. Thus, we conclude that deferoxamine may exert a protective action against the dysfunction of neonatal mammalian hearts induced by preservation-reperfusion through an inhibition of iron-catalyzed radical formation.