The effects of on-pump and off-pump coronary artery bypass surgery on oxidative stress and cerebral oxygenation: a prospective observational study.

Background/aim: In this prospective observational study, our goal was to investigate the relationship between serum levels of oxidative stress (OS) parameters and regional cerebral oxygen saturation (rSO2) in addition to evaluating postoperative clinical outcomes among patients undergoing coronary artery bypass graft surgery (CABG). Materials and methods: This study comprised 64 adult patients undergoing elective CABG (on-pump [n = 48] and off-pump [n = 16]) procedures. Serum OS levels and rSO2 values were measured intraoperatively at three specific time points: T1 (after induction), T2 (15 min before aortic cross-clamp removal or the final distal anastomosis), and T3 (15 min after aortic cross-clamp removal or the last distal anastomosis). Results: Serum OS and lactate values demonstrated higher levels at T2 and T3 (p < 0.001), while rSO2 values were lower at T2 (p = 0.024) in the on-pump CABG group compared to the off-pump CABG group. The rSO2 values at T2 exhibited a negative correlation with OS parameters, lactate levels at T2 and T3, aortic clamp time, postoperative mechanical ventilation time, and intensive care unit stay length. In the multivariate linear regression analysis (R2 = 0.181, p = 0.001), lactate values at T2 emerged as the sole factor affecting the OS index at T2 (t = 2.843, p = 0.006). Conclusion: In our study, we observed elevated OS values and relatively low rSO2 values during on-pump CABG procedures, with rSO2 showing an association with increased OS parameters. Close monitoring of the OS response level and rSO2 during CABG could potentially enhance postoperative clinical outcomes.

Early and Mid-Term Outcomes of Delayed Sternum Closure Strategy in Adult Cardiac Surgery: A Single-Center Experience.

BACKGROUND: Delayed sternum closure is a crucial strategy in the management of hemodynamic instability after weaning from cardiopulmonary bypass. This study aimed to evaluate our outcomes with this technique in light of the literature. METHODS: We retrospectively reviewed the data of all the patients who developed postcardiotomy hemodynamic compromise and intraaotic balloon pump was inserted between November 2014 to January 2022. Patients were divided into two groups: primary sternal closure group, and delayed sternum closure group. Patients' demographic data, hemodynamic parameters, and postoperative morbidities were recorded. RESULTS: Delayed sternum closure was performed in 16 patients with an incidence of 3.6%. The most common indication was hemodynamic instability in 14 patients (82%), followed by arrhythmia in 2 patients (12%) and diffuse bleeding in 1 patient (6%). The mean time to sternum closure was 21 (±7) hours. Three patients died (19%), p > 0.999. The median follow-up period was 25 months. Survival analysis revealed that the survival rate was 92%, p = 0.921. Deep sternal infection was observed in one patient with (6%), p > 0.999. multivariate logistic regression analysis revealed that end-diastolic diameter [odds ratio (OR) 4.5, 95% CI (1.19-17), p = 0.027], right ventricle diameter [OR 3.9, 95% CI (1.3-10.7), p = 0.012] and aortic clamp time [OR 1.16, 95% CI (1.02-1.12), p = 0.008] were independent risk factors for delayed sternum closure. CONCLUSIONS: Elective delayed sternal closure is a safe and effective method for treating postcardiotomy hemodynamic instability. It can be performed with a low incidence of mortality and sternal infections.

A Right Ventricular Mass With Intracavitary Obliteration: Tumor or Thrombus?

A 47-year-old woman was admitted to the hospital because of dyspnea for the past three months. She was previously diagnosed with pulmonary embolism. She had been operated on for a colon tumor five years ago and no residual cancer was detected on oncological follow-up. Her transthoracic echocardiographic and transesophageal echocardiographic evaluation showed a hypertrophic right ventricle occupied by a 2.7 x 4.8 cm immobile mass obliterated to the right ventricle cavity. All the non-invasive tests were consistent with thrombus prediagnosis. She underwent surgery. Mass was resected from the right ventricle as much as possible. Histopathology of surgical material revealed metastatic spindle cell adenocarcinoma. We aim to increase the awareness of the differential diagnosis of thrombus or tumor, thereby leading to appropriate management.

Cardiovascular Surgeons' Medical Perspectives Regarding Social Media Usage: a Survey Analysis.

INTRODUCTION: We aimed to evaluate the use of social media among cardiovascular surgery specialists and their respective perspectives. METHODS: In total, 173 cardiovascular surgeons were reached through an online survey. The surgeons surveyed were cardiovascular surgery specialists. The questionnaire consisted of 33 questions, including closed-ended and open-ended questions about social media. RESULTS: We found that 73.4% of the participants think that social media facilitates the communication of the patient with the doctor, and 87.9% think that social media increases the publicity of the physician. Furthermore, 80.9% of the participants believe that informing through social media creates information pollution. We found that personal use of Instagram was more common in state hospital cardiac surgeons. The number of patients who contacted surgeons in private hospital for surgery via social media were found to be statistically significant, and it was found that this group benefitted more economically. CONCLUSION: Social media usage rates of cardiovascular surgeons were found to be high. On the other hand, it was observed that the rate of surgeons who share medical content is low. However, half the cardiovascular surgeons who participated in the study believe that their colleagues do not fully comply with the ethical rules in medical sharing.

Decreased brain-derived neurotrophic factor levels may predict early perioperative neurocognitive disorder in patients undergoing coronary artery bypass surgery: A prospective observational pilot study.

STUDY OBJECTIVE: To determine the prognostic value of the change in intraoperative BDNF (Brain-derived neurotrophic factor) levels during cardiac surgery with cardiopulmonary bypass (CPB) on early perioperative neurocognitive disorder (PND). DESIGN: Prospective observational pilot study. SETTING: The study was performed in the Medical Faculty Hospital, from January 2020 to August 2020. PATIENTS: 45 adult patients undergoing elective coronary artery bypass surgery (CABG) with CPB. INTERVENTIONS: None. MEASUREMENTS: Cognitive function was evaluated 1 day before and 4 days after the surgery. Serum BDNF levels were measured at four time points (T1: after induction; T2: with aortic cross-clamp; T3: without aortic cross-clamp; T4: 4 days after surgery) by enzyme-linked immunosorbent assay. MAIN RESULTS: The incidence of PND was 37.8% four days after surgery. Serum BDNF (T2 and T4) levels were significantly lower in PND group compared to non- PND group (p = 0.003 and p = 0.016, respectively). Moreover, lactate, rSO2 (regional cerebral oxygen saturation), aortic cross-clamp time, CPB duration, and the amount of blood transfusion differed between the groups. Logistic regression analysis identified serum BDNF-T2, age, cross-clamp time, and rSO2-T2 as independent risk factors for PND. Based on the ROC analysis, the area under curve (AUC) of BDNF-T2 concentration for prediction of PND was 0.759 with sensitivity of 71.4% and specificity of 64.7% (p < 0.01). CONCLUSION: Intraoperative BDNF serum levels may be a useful biomarker in predicting PND in patients undergoing CABG surgery. More comprehensive studies is needed in order to confirm the effect of decreasing intraoperative BDNF serum levels on the development of PND. TRIAL REGISTRATION NUMBER: NCT04250935 www.clinicaltrials.gov.

Evaluation of Neurocognitive Abilities in Patients Undergoing Carotid Endarterectomy Surgery.

OBJECTIVE: To evaluate the differences in neurocognitive abilities between the preoperative and postoperative periods following carotid endarterectomy (CEA), due to carotid artery stenosis, and to evaluate the effectiveness of CEA on neurocognitive abilities in the future. MATERIAL AND METHODS: Thirty-eight cases of CEA surgery at Bozok University Faculty of Medicine Research Hospital between January 2015 and June 2020 were examined. Neurocognitive tests were performed on carotid endarterectomy patients one day before the operation and on the 2nd, 4th, and 30th postoperative days. The effect of CEA on cognitive results has been investigated. RESULTS: Of the patients, eight were female (21.1%), 30 were male (78.9%), and the mean age was 66 ± 4.09. Thirty-two (84.21%) of the patients were operated on under general anesthesia and six (15.78%) under regional anesthesia. A shunt was used in 19 patients. Right carotid endarterectomy was performed in 20 cases and left carotid endarterectomy in 18 cases. We used the primary closure technique in two of 38 cases and patches on 36 of them. We used Dacron in 21 cases, PTFE in 12 cases, and saphenous vein as a patch in three cases. In the WMS digit spam and recall scores, the postoperative period fell on the 2nd day, and then on the 4th and 30th day after the operation, there was a low level of increase over time. Compared with the preoperative period, the learning score was found to be the lowest on the 2nd day, lower on the 4th day compared with the preoperative period and improved compared with the preoperative period on the 30th day. There was no decrease in the verbal fluency test score results after the operation, on the contrary, it was observed minimally. The test score results cumulatively were decreased in the early postoperative periods compared with the preoperative period and increased on the 30th day compared with the preoperative period. CONCLUSION: The purpose of CEA in the past was the prevention of ischemic stroke and cerebrovascular disease (CVD) rather than neurocognitive recovery. Factors affecting neurocognition in CEA are multifactorial. Preservation and improvement of neurocognition are more important than any other period of history. By prioritizing cognitive abilities in the treatment of carotid stenosis, individualization of the treatment will help maximize the increase in cognitive abilities by providing optimum benefit to the patient of each factor.

A simultaneous coronary artery bypass grafting on beating heart and right upper lobectomy in a patient with a lung adenocarcinoma.

A coexisting coronary heart disease may increase the operative mortality and morbidity rates of lung resection. A simultaneous or a two-stage procedure using myocardial revascularization prior to the pulmonary resection may reduce the postoperative morbidity and mortality. Herein, we present a 65-year-old male case of a lung adenocarcinoma in whom a simultaneous coronary artery bypass grafting on a beating heart and right upper lobectomy was performed.

Tricuspid Valve Replacement Through Right Thoracotomy has Better Outcomes in Redo Cases.

BACKGROUND: The tricuspid valve is usually ignored and tricuspid interventions are mostly done in the context of other planned cardiac surgery. Isolated tricuspid reoperative procedure, especially tricuspid valve replacement (TVR) is very rare and carries a very high mortality rate. In this prospective study, clinical results of isolated TVR either through a median re-sternotomy or an antero-lateral thoracotomy with conventional cardiopulmonary bypass (CPB) have been evaluated. METHODS: Thirty patients with previous open heart surgery through median sternotomy had isolated TVR between 2004 and 2011. Operative approaches were through a median re-sternotomy in 13 patients and a right antero-lateral thoracotomy in 17 patients. RESULTS: Follow-up period is complete with a mean duration of 19.77±17.08 months. The hospital mortality rates were 46.2% (six patients) in the Median Re-sternotomy Group and 5.9% (one patient) in the Thoracotomy Group (p= 0.025). The surgical procedures lasted shorter and the postoperative drainage amounts were lower in the Thoracotomy Group (298.08±76.64min vs 246.76±47.40min, p= 0.032 and 1787.50±1399.53mL vs 903.33±692.43mL, p= 0.03 respectively). Presence of ascites in the preoperative period (p= 0.007), operative technique (median re-sternotomy) (p= 0.025), use of cross-clamp (p= 0.048), and need for inotropic support during the operation (p= 0.002) were statistically significant factors affecting the hospital mortality. The mean estimated life period was better for the Thoracotomy Group (16.7±5.03 versus 35.9±5.01 months, p= 0.044). Presence of ascites in the preoperative period was a significant risk factor for overall mortality according to Cox regression analysis. CONCLUSION: Thoracotomy for TVR in patients with previous median sternotomy is a practical and safe technique with lower mortality rates.

Coronary artery bypass grafting in the octogenarians: should we intervene, or leave them be?

OBJECTIVE: Coronary artery bypass grafting (CABG) is gradually increasing in the elderly population. We aimed to investigate the risk factors and the results of CABG along with the long term survival in patients at an age of 80 and older. METHODS: Between January 2002 and December 2011, a total of 101 consecutive patients at an age of 80 and older who underwent CABG in our hospital were included in the study. The patients were followed and the long-term survival was estimated. RESULTS: The mean age of the patients was 82.98 ± 2.27 years. Sixty-four (63.4%) were males and 37 (36.6%) were females. Emergency surgery, duration of cardiopulmonary bypass, the intensive care unit (ICU) stay, inotropic support, intra aortic balloon pulsation application, amount of erythrocyte transfusion and fresh frozen plasma transfusion and ventilation period were significantly higher in the patients who died in the hospital. The duration of cardiopulmonary bypass (CPB) was found to be an independent predictor of mortality (OR: 1.18, 95% CI 1.01-1.38, P = 0.034). The in-hospital mortality was 16.8%. Kaplan-Meier analyses revealed a survival ratio of 91.3% at one year, 82.9% at three years and 69.0% at five years. CONCLUSIONS: Patients at the age of 80 and older can be candidates for the CABG procedure bearing in mind that they may have a longer ventilation period and intensive care unit stay. The morbidity and mortality of this age group is considered within an acceptable range. Approaches to minimize CPB, or the choice of off-pump surgery, may be a preventive method to lower the incidence of mortality. Hence, CABG may be performed in this age group with a satisfactory survival ratio.

Assessment of Radial Artery Graft Patency in Symptomatic Patients.

BACKGROUND: The purpose of this study is to evaluate the patency of radial artery (RA) grafts consistent with the target vessel characteristics. METHODS: Between October 2001 and January 2012, 83 symptomatic patients or patients with positive ischemic test results underwent coronary angiography following coronary artery bypass grafting. Of these, 68 patients with 81 RA grafts at a mean 49.2 ± 31.9 months (range, 1-137 months) were evaluated. According to the location and degree of proximal stenosis, 5-year graft patency was determined by Kaplan-Meier analysis. The relationships between RA graft patency and degree of proximal stenosis, target vessel location, and inflow characteristics of grafts were assessed by means of Cox proportional hazard models. RESULTS: Mean age of the patients was 56.4 ± 10.2 years. The period between the operation and postoperative coronary angiography was 49.2 ± 31.9 months (range, 1-137 months; median, 48.8 months). There was no impact on RA patency with regard to preoperative characteristics of the patients. RA patency was higher for left coronary system compared with right system (p = 0.038; 85.5 vs. 65.4%). In addition, patency rate was statistically higher for the proximal stenosis ≥ 90% (odds ratio, 3.65; 95% confidence interval, 1.20-11.07; p = 0.018). Kaplan-Meier patency analysis showed a patency of RA as 79.2% at 5 years. CONCLUSION: RA graft patency differs with degree of preoperative native coronary artery stenosis and location of target vessel. RA grafts to not severely stenosed (< 90%) coronary system and to the right coronary territory carry a remarkably high risk of graft failure.

Diagnostic accuracy of Doppler ultrasonography for assessment of internal thoracic artery graft patency.

OBJECTIVE: The main purpose of this study was to assess the patency of left internal thoracic artery (LITA) graft by using color Doppler ultrasonography (CDUSG) and furthermore to determine the sensitivity and specificity of CDUSG for patency by using coronary angiography as the reference standard. METHODS: This study is an observational cohort study on diagnostic accuracy that was held between August 2008 and October 2009. CDUSG was performed in 138 consecutive patients who had angina symptom or positive ischemic findings following coronary artery bypass surgery. LITA blood flow velocity at peak-systole (PSV), diastole (PDV) and end-diastole (EDV) was recorded. All patients were also assessed by coronary angiography for LITA graft patency. Statistical analysis was performed by using independent samples t-test, Mann-Whitney U test, chi-square test and receiver operating curve analyses (ROC). RESULTS: Seventy-eight of all patients had functional LITA grafts and 59 patients had dysfunctional LITA grafts according to CDUSG-derived parameters, whereas we cannot conclude about one patient's LITA graft functionality. The LITA grafts were visualized angiographically in all cases. Of all 138 patients, 60 patients had dysfunctional LITA grafts after angiographic evaluation. The ROC analyses showed that PDV (AUC=0.899, 95% CI 0.844 to 0.953; p<0.001) and EDV (AUC=0.900; 95% CI 0.847 to 0.953; p<0.001) values were also strongly associated with graft functionality. We found out that CDUSG predicts LITA graft functionality with a sensitivity and specificity of 100% and 98.4% respectively. The accuracy of the CDUSG was calculated as 99.3%. CONCLUSION: CDUSG is a reliable non-invasive method for assessment of LITA graft patency.

Effectiveness of prophylactic levosimendan in high-risk valve surgery patients.

OBJECTIVE: Levosimendan has anti-ischaemic effects, improves myocardial contractility and increases systemic, pulmonary and coronary vasodilatation. These properties suggest potential advantages in high-risk cardiac valve surgery patients where cardioprotection would be valuable. The present study investigated the peri-operative haemodynamic effects of prophylactic levosimendan infusion in cardiac valve surgery patients with low ejection fraction and/or severe pulmonary arterial hypertension. METHODS: Between May 2006 and July 2007, 20 consecutive patients with severe pulmonary arterial hypertension (systolic pulmonary artery pressure ≥ 60 mmHg) and/or low ejection fraction (< 50%) who underwent valve surgery in our clinic were included in the study and randomised into two groups. Levosimendan was administered to 10 patients in group I and not to the 10 patients in the control group. Cardiac output (CO), cardiac index (CI), systemic vascular resistance (SVR), pulmonary vascular resistance (PVR) and mean pulmonary artery pressure (MPAP) were recorded for each patient preoperatively and for 24 hours following the operation. RESULTS: CO and CI values were higher in the levosimendan group during the study period (p < 0.05). MPAP and PVR values were significantly lower in the levosimendan group for the 24-hour period (p < 0.05) and SVR values were significantly lower after 24 hours in both groups. When clinical results were considered, no difference in favour of levosimendan was detected regarding the mortality and morbidity rates between the groups. CONCLUSION: Levosimendan improved the haemodynamics in cardiac valve surgery patients with low ejection fraction and/or severe pulmonary arterial hypertension, and facilitated weaning from cardiopulmonary bypass in such high-risk patients when started as a prophylactic agent.

Comparison of neurocognitive functions after beating-heart mitral valve replacement without aorta cross-clamping and after standard mitral valve replacement with cardioplegic arrest.

BACKGROUND: The aim of this study was to compare the postoperative long-term neurocognitive functions of patients who under-went beating-heart mitral valve replacement on cardiopulmonary bypass (CPB) without aorta cross-clamping with those of patients who underwent mitral valve replacement via the classic method. METHODS: The study group included 25 randomly selected patients who underwent beating-heart mitral valve surgery. During the same period, 25 patients were randomly selected as controls to undergo mitral valve replacement procedures via the standard ascending aorta-cannulation technique. The clinical and postoperative (2 months) neurocognitive functional data of both groups were compared. RESULTS: Neurologic deficit was observed in neither group during the postoperative period. There were no statistically significant differences between the control and the study groups with respect to Hospital Anxiety and Depression Scale (HADS) results (HADS: anxiety, P = .653; HADS: depression, P = .225), in the right hemispheric cognitive function test results (Raven's Standard Progressive Matrices [RSPM] and Line Orientation Test [LOT] tests: RSPM, P = .189), and in the left hemispheric cognitive function test results (the Ray Auditory Verbal Learning [RAVL] and Stroop Color-Word Test [SCWT] tests: SCWT 1 time, P = .300; SCWT 2 time, P = .679; SCWT 3 time, P = .336; SCWT 4 time, P = .852; SCWT 5 time, P = .416; RAVL total verbal learning, P = .167; RAVL immediate recall, P = .791; RAVL distraction trial, P = .199; RAVL retention, P = .174; RAVL delayed recall, P = .111; RAVL recognition, P = .282; SCWT 4 mistake, P = .306; SCWT 4 reform, P = .066; SCWT 5 mistake, P = .236; SCWT 5 reform, P = .301). CONCLUSIONS: The technique of mitral valve replacement with normothermic CPB without cross-clamping of the aorta may be safely used for the majority of patients requiring mitral valve replacement without causing deterioration in neurocognitive functions.

Does on-pump normothermic beating-heart valve surgery with low tidal volume ventilation protect the lungs?

BACKGROUND: Postoperative pulmonary dysfunction following cardiopulmonary bypass (CPB) usually develops secondary to the inflammatory process with contact activation, hypothermia, operative trauma, general anesthesia, atelectasis, pain, and pulmonary ischemia/reperfusion due to cross-clamping. The aim of the present study was to evaluate the effects of an on-pump, normothermic, and beating-heart technique and of low-volume ventilation on lung injury. METHODS: We compared the results for 20 patients who underwent operations with an on-pump, normothermic, and beating-heart technique of mitral valve surgery with low-volume ventilation (group 1) with the results for 23 patients who underwent their operations with an on-pump, hypothermic cardiac-arrest technique (group 2). In both groups, blood samples were collected from the right superior pulmonary vein, and inflammation and oxidative stress markers (malondialdehyde, lactic acid, platelet-activating factor, and myeloperoxidase) were studied. RESULTS: Malondialdehyde, myeloperoxidase, and lactate values were significantly lower in group 1 than in group 2 just before the termination of CPB (P < .05). We observed no differences between the 2 groups with regard to values for platelet-activating factor. CONCLUSIONS: Inflammation and oxidative stress markers were lower in the group of patients who underwent beating-heart valve surgery with low-volume ventilation. These results reflect less of an ischemic insult and lower inflammation compared with the results for the patients who underwent conventional operations.

Beating heart versus conventional mitral valve surgery.

OBJECTIVES: The present study aimed to compare the results of beating heart technique and conventional mitral valve surgery (MVS). METHODS: Three hundred and nineteen patients who underwent MVS between April 2005 and December 2006 were enrolled in the study. While 125 patients underwent beating heart MVS (group 1), the conventional approach was used for 194 patients (group 2). Of those patients who underwent beating heart MVS, 75 underwent MVS without cross-clamping the aorta. Coronary sinus retroperfusion was used during surgery in the remaining 50 patients. The right anterolateral thoracotomy was performed in nine out of the 29 patients requiring re-operation, while resternotomy was performed in 20. RESULTS: No significant differences were shown between the groups in the preoperative period in terms of the Parsonnet mortality score, Ontario mortality score, and length of intensive care stay. However, there were significant differences with respect to EuroSCORE risk score, EuroSCORE mortality, and Parsonnet risk score, and length of hospital stay according to Ontario risk scoring. It was established that the patients in group 1 had a shorter length of hospital stay [group 1: six days (range, 4-37 days); group 2: 10 days (range, 4-62 days)]. Group 1 was observed to have shorter time periods when the groups were compared regarding operative time [group 1: 130 min (range, 100-270 min); group 2: 240 min (range, 100-360 min)], cross-clamping (XCL) time [group 1: 27.5 min (range, 3-99 min); group 2: 60.5 min (range, 30-163 min)], and cardiopulmonary bypass time [group 1: 57 min (range, 22-150 min); group 2: 90 min (range, 39-388 min)]. There were also significant differences in favor of group 1 in terms of postoperative need for inotropic support [group 1: 26 patients (16%); group 2: 68 patients (35%)]. Although there were no statistically significant differences in the groups in terms of mortality rates according to the Parsonnet scoring system, with the exception of the moderate risk group, it was noted that the mortality rates in the beating heart group were lower. CONCLUSIONS: This study concluded that beating heart MVS can be performed successfully, particularly for patients at higher risk which will lead to increased morbidity and mortality in postoperative period.

Treatment of mechanical aortic valve thrombosis: fibrinolytic treatment versus surgical intervention: result of eight cases.

OBJECTIVE: : Thrombosis of mechanical heart valve prosthesis is a rare fatal complication after heart valve replacement. Although surgical intervention is the suggested treatment in many series, fibrinolytic treatment offers a good alternative. We describe eight cases with mechanical aortic valve thrombosis and compare their results after fibrinolytic treatment or redo aortic valve replacement. METHODS: : Between February 2008 and March 2009, eight patients with previous mechanical prosthetic aortic valve replacement history were admitted to our center with mechanical aortic valve thrombosis. Four patients were operated, and the remaining four patients received low-dose fibrinolytic treatment. All patients' data were collected prospectively. RESULTS: : Two of the four operated patients died. In the fibrinolytic group, all patients totally recovered, and there was no mortality or morbidity during the follow-up period. CONCLUSIONS: : We thought that fibrinolytic treatment is a feasible and effective method for thrombosed mechanical aortic valve. However, much more populated patient groups are needed for the vigorous inference.

Levosimendan and severe pulmonary hypertension during open heart surgery.

Weaning from cardiopulmonary bypass is the most important stage during mitral valve surgery, especially in patients with severe pulmonary hypertension. We report two patients with severe pulmonary hypertension who were operated on because of valvular heart disease. To reduce the pulmonary artery pressure, levosimendan was used because of its vasodilatory and cytoprotective effects. All patients tolerated the operation and levosimendan administration. Their postoperative course was uneventful. Levosimendan can be used to treat pulmonary hypertension during operations for heart valve disease. Patients clearly benefit from the vasodilator action of the drug for reducing pulmonary artery pressure.