Toshiro Inaba

Introns in protein-coding genes in Archaea

Introns in protein‐coding genes are ubiquitous in eukaryotic cells, but pre‐mRNA splicing has yet to be reported in archaeal and its viral genomes. We present evidence of introns in genes encoding a homolog of eukaryotic Cbf5p (centromere‐binding factor 5; a subunit of a small nucleolar ribonucleoprotein) in three Archaea; Aeropyrum pernix, Sulfolobus solfataricus and Sulfolobus tokodaii. Splicing of pre‐mRNAs in vivo was demonstrated by reverse transcriptase‐mediated polymerase chain reaction. The exon–intron boundaries of these genes are predicted to be folded into a structure similar to the bulge–helix–bulge motif, suggesting that splicing of these pre‐mRNAs probably depends on the splicing system elucidated for archaeal pre‐tRNAs and rRNAs.

Aortic Insufficiency in Patients With Sustained Left Ventricular Systolic Dysfunction After Axial Flow Assist Device Implantation

BACKGROUND Predicting the occurrence of aortic insufficiency (AI) during left ventricular assist device (LVAD) support has remained unsolved. METHODS AND RESULTS We enrolled 52 patients who had received continuous flow LVAD (14 axial and 38 centrifugal pumps) and who been followed for ≥6 months between Jun 2006 and Dec 2013. Native aortic valve (AV) opening was observed in 18 patients (35%) with improved LV systolic function, and none of them had AI. On multivariate logistic regression analysis preoperative shorter heart failure duration was the only independent predictor of postoperative native AV opening (P=0.042; odds ratio [OR], 0.999). Of the remaining 34 patients (65%) with closed AV, 11 had AI with enlargement of the aortic root and narrow pulse pressure. Among those with closed AV, axial pump use (n=13) was the only significant predictor of the development of AI (P=0.042; OR, 4.950). Patients with AI had lower exercise capacity and a higher readmission rate than those without AI during 2-year LVAD support (55% vs. 8%; P<0.001). CONCLUSIONS Native AV opening during LVAD support is profoundly associated with reversal of LV systolic function, especially in patients with preoperative shorter heart failure duration. Among those in whom the native AV remains closed, low pulsatility of axial flow pump may facilitate aortic root remodeling and post-LVAD AI development that results in worse clinical outcome.

Bosentan improved persistent pulmonary hypertension in a case after implantation of a left ventricular assist device

No medical treatment has been established to ameliorate pulmonary hypertension (PH) due to left heart disease. Heart transplantation (HTx) is thus far the definitive therapy for stage D heart failure, but concomitant PH is one of the major risk factors for death after HTx. Recently, implantation of a left ventricular assist device (LVAD) has been reported to improve PH and has become a major bridge tool for HTx. We experienced a rare case with persistent PH even after the implantation of a continuous-flow LVAD. The administration of an endothelin receptor antagonist, bosentan, significantly decreased pulmonary vascular resistance. Combination therapy with LVAD implantation and anti-PH medication may be useful for patients with stage D heart failure complicated with severe PH.

Platelet-Derived Growth Factor Receptor-Tyrosine Kinase Inhibitor, Imatinib, Is Effective for Treating Pulmonary Hypertension Induced by Pulmonary Tumor Thrombotic Microangiopathy

Pulmonary hypertension (PH) induced by pulmonary tumor thrombotic microangiopathy (PTTM) can be fatal because its rapid progression confounds diagnosis, and it is difficult to control with therapy. Here we describe a woman with symptomatic PTTM-PH accompanying gastric cancer that was suspected from perfusion scintigraphy. PTTM-PH was diagnosed by gastroesophageal endoscopy and lung biopsy after partial control of PH using the platelet-derived growth factor (PDGF) receptor (PDGFR) tyrosine kinase inhibitor, imatinib. Treatment with sildenafil and ambrisentan further decreased PH, and she underwent total gastrectomy followed by adjuvant TS-1 chemotherapy. PH did not recur before her death from metastasis. Postmortem histopathology showed recanalized pulmonary arteries where the embolized cancer masses disappeared. PDGF-A, -B, and PDGFR-α, β expression was detected in cancer cells and proliferating pulmonary vascular endothelial cells. Thus, PTTM-PH was successfully controlled using a combination of imatinib, drugs to treat pulmonary arterial hypertension, and cancer management.

Parasympathetic Reinnervation Accompanied by Improved Post-Exercise Heart Rate Recovery and Quality of Life in Heart Transplant Recipients

Although sympathetic reinnervation is accompanied by the improvement of exercise tolerability during the first years after heart transplantation (HTx), little is known about parasympathetic reinnervation and its clinical impact. We enrolled 21 recipients (40 ± 16 years, 71% male) who had received successive cardiopulmonary exercise testing at 6 months, and 1 and 2 years after HTx. Exercise parameters such as peak oxygen consumption or achieved maximum load remained unchanged, whereas recovery parameters including heart rate (HR) recovery during 2 minutes and the delay of peak HR, which are influenced by parasympathetic activity, improved significantly during post-HTx 2 years (P < 0.05 for both). HR variability was analysed at post-HTx 6 months in 18 recipients, and high frequency power, representing parasympathetic activity, was significantly associated with the 2 recovery parameters (P < 0.05 for all). We also assessed quality of life using the Minnesota Living with Heart Failure (HF) Questionnaire at post-HTx 6 months and 2 years in the same 18 recipients, and those with improved recovery parameters enjoyed a better HF-specific quality of life (P < 0.05 for both). In conclusion, parasympathetic reinnervation emerges along with improved post-exercise recovery ability of HR and quality of life during post-HTx 2 years.

Novel scoring system using postoperative cardiopulmonary exercise testing predicts future explantation of left ventricular assist device

BACKGROUND Although cardiopulmonary exercise (CPX) testing is an established tool for predicting survival in patients with heart failure (HF), its prognostic impact on explantation of left ventricular assist device (LVAD) was unknown. METHODS AND RESULTS: We enrolled 33 patients who had undergone implantation of extracorporeal pulsatile flow LVAD and symptom-limited CPX testing at 3 months after operation, and who were followed between 2005 and 2014. Patients who received conversion to continuous flow LVAD were excluded. On Cox regression analysis, E1 (maximum load ≥51W; HR, 27.55), E2 (minute ventilation/carbon dioxide output [V̇E/V̇CO2] slope ≤34; HR, 16.86), and E3 (peak oxygen consumption [PV̇O2] ≥12.8 ml·kg(-1)·min(-1); HR, 18.35) significantly predicted explantation expectancy during 2 years after LVAD implantation (P<0.05 for all). Explantation score, the sum of positive E1-3, significantly stratified 2-year cumulative explantation rate into low (0 points), intermediate (1-2 points), and high (3 points) expectancy groups (0%, 29%, and 86%, respectively, P<0.001). When the scoring system was used for 45 patients with continuous flow LVAD, the 2 patients who had explantation were assigned to the high expectancy group. CONCLUSIONS Explantation score, calculated simply from 3 postoperative symptom-limited CPX testing parameters, is a novel tool to predict explantation expectancy of LVAD and to select good candidates for the weaning test.

How to demonstrate the reversibility of end-organ function before implantation of left ventricular assist device in INTERMACS profile 2 patients?

For the time being, in Japan, two recently approved implantable ventricular assist devices (VADs) are indicated only when a patient has been listed for heart transplantation or approved to be eligible for heart transplantation by in-hospital committee. The reversibility of end-organ dysfunction must be expected before VAD implantation, but it is often hard to prove during worsening clinical status. We report two patients whose end-organ dysfunction had been eventually demonstrated to be reversible by invasive procedures such as transluminal liver biopsy or transient insertion of intra-aortic balloon pumping.

Is the internal jugular vein or femoral vein a better approach site for endomyocardial biopsy in heart transplant recipients

Scheduled serial endomyocardial biopsies are executed by an internal jugular vein (IJV) or femoral vein (FV) approach to survey acute rejection after heart transplantation (HTx). However, a better approach site is needed. A total of 379 sessions consisting of 329 IJV approaches and 50 FV approaches in 48 HTx recipients executed at 75 ± 127 days (41182 days) after HTx between September 2007 and April 2014 at University of Tokyo Hospital were retrospectively analyzed. The IJV approach had shorter operation and radiation exposure times, and a lower dose of radiation exposure and lower usage of contrast agents than the FV approach (all P < 0.001). There were no fatal complications requiring surgical management or resulting in death during all sessions. The IJV approach had less complications than the FV approach (2.7% versus 10.0%, P = 0.011). Among the complications, atrial tachyarrhythmia occurred only with the IJV approach (0.9%), whereas transient ventricular tachyarrhythmia and bundle branch block were more frequently observed in the FV approach (8.0% versus 0.9%, P = 0.042). In conclusion, endomyocardial biopsy from the IJV approach was safer and less invasive than that of the FV approach if we only consider the incidence of atrial tachyarrhythmia.

Targeted therapy is required for management of pulmonary arterial hypertension after defect closure in adult patients with atrial septal defect and associated pulmonary arterial hypertension.

BACKGROUND Therapeutic strategies for pulmonary arterial hypertension (PAH) associated with atrial septal defect (ASD) remain a matter of debate. METHODS AND RESULTS We identified 5 outpatients who had been diagnosed with ASD-PAH and undergone ASD closure in combination with targeted therapy with certified PAH drugs. We assessed changes in hemodynamic parameters and exercise capacity. The combination of ASD closure and targeted therapy significantly increased systemic blood flow (Qs) from the baseline (from 3.3 ± 0.6 L/minute to 4.2 ± 1.0 L/minute, P < 0.05) with a significant improvement in the World Health Organization Functional Class (WHO-FC; from 2.8 ± 0.4 to 1.6 ± 0.5, P < 0.05). The hemodynamic data before and after ASD closure without targeted therapy showed further elevation of pulmonary vascular resistance shortly after ASD closure (678 dyne · s/cm(5) to 926 dyne · s/cm(5)) in 1 case, as well as after a long time since ASD closure (491.0 ± 53.7 dyne · s/cm(5) to 1045.0 ± 217.8 dyne · s/cm(5)) in 2 cases. This worsening was reversed after the targeted therapy, accompanied by an increase in Qs and an improvement in WHO-FC in all cases. CONCLUSIONS Targeted therapy should be added to ASD closure in adult patients with ASD-PAH.

Novel Scoring System Using Cardiopulmonary Exercise Testing Predicts Prognosis in Heart Failure Patients Receiving Guideline-Directed Medical Therapy

BACKGROUND Among variables obtained from cardiopulmonary exercise testing (CPXT), peak oxygen consumption (PV̇O2) and the minute ventilation vs. carbon dioxide output (V̇E vs. V̇CO2) slope were established as predictors of death of patients with heart failure (HF) at the cutoff points of 14 ml·min(-1)·kg(-1)and 34, respectively. However, a recent update of guideline-directed medical treatment (GDMT) might alter the implication of these variables. METHODS AND RESULTS We enrolled 77 HF patients receiving GDMT who had undergone symptom-limited CPXT between 2006 and 2014. Among them, 29 patients were re-hospitalized for HF and there were 13 cardiac deaths during the 4-year study period. Cox regression analyses demonstrated that the V̇E vs. V̇CO2slope, peak heart rate, peak systolic blood pressure, and PV̇O2were significant predictors of both re-admission and cardiac death at each cutoff point calculated by receiver-operating characteristic analyses. A new scoring system was constructed using the following criteria: 1 point was assigned to a variable meeting the cutoff point for re-admission; 2 points were assigned to that for cardiac death. The total scores calculated as the summation of each point (range, 0-8 points) had significantly highest area under the curves compared with each CPXT variable (P<0.05), and significantly stratified both event-free rate into 3 groups (P<0.05). CONCLUSIONS A novel scoring system using 4 CPXT variables simultaneously predicted re-admission and cardiac death even in patients with HF receiving GDMT.