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Biomedical subjects

A Johan

Publications and source records attributed to A Johan.

At least 19 recordsLinked to original sources
PubMed2004

A stent is not just a stent: Stent construction and design do matter in its clinical performance.

The undisputed superiority of stents over conventional balloon angioplasty has resulted in a plethora of stents in clinical use. Recent data, however, have indicated not all stent models are the same. Nuances in stent design and construction have impacted significantly on the immediate and long-term clinical outcome. Among the stainless steel stents, those with multicellular or tubular designs have proven to be superior to coiled or hybrid stent models, and thin-strut stents perform better than thicker-strut stents. Coating stainless steel stents with gold, carbide, phosphorylcholine or heparin do not appear to confer any additional benefit, compared with bare metal stents. In contrast, randomised trials have demonstrated that drug-eluting stents coated with various anti-proliferative drugs, with or without a carrier polymer, afford unparalleled restenosis rates compared with non-drug-eluting stents. Drug-eluting stents, however, are expensive, and their long-term durability and safety remain undefined. Notwithstanding these unresolved issues, it is likely that the majority of percutaneous coronary interventions will involve the use of drug-eluting stents once a more attractive balance between their cost and clinical effects is reached.

Angioplasty, Balloon, Coronary↗
PubMed2002

Cardiac output increases prior to development of pulmonary edema after re-expansion of spontaneous pneumothorax.

Pulmonary edema following reexpansion of spontaneous pneumothorax is an uncommon complication. The underlying mechanism of this condition is unclear. We report the hemodynamic characteristics in a series of 7 male patients with spontaneous large (>50%) pneumothoraces of > or = 24 h and correlate the changes with reexpansion pulmonary edema (REPE). A pulmonary artery floatation catheter was inserted and hemodynamic data were obtained before therapeutic chest tube insertion, 1 h after chest tube insertion and the following day. Four (57%) patients developed REPE. There was a tendency for larger pneumothorax to develop REPE. Capillary wedge pressure did not change significantly 1 h after the insertion of chest tube in all our patients. Cardiac output increased significantly in patients who developed REPE compared to those who did not (+ 1.06 l/min vs -0.27 l/min; P = 0.03) 1 h after insertion of chest tube. One patient did not develop pulmonary edema despite having a large (> 80%) pneumothorax. His cardiac output did not rise 1 h after chest tube insertion. REPE is not an uncommon complication following chest tube drainage in patients with large and long-standing pneumothorax. The increase in cardiac output after chest tube insertion may be associated with subsequent development of REPE.

Adult↗
PubMed2002

Unplanned extubation: a local experience.

OBJECTIVES: To study the outcome of unplanned extubation (UE) in the Medical Intensive Care Unit (MICU) and to identify factors which predict the need for reintubation. METHODS: A prospective study of all mechanically ventilated patients admitted to MICU in 1998. Patients were enrolled into the study at the point of their first UE. The primary endpoint was reintubation after UE and secondary endpoint was death from any cause during hospitalisation. RESULTS: A total of 543 patients were admitted to MICU of which 312 were mechanically ventilated. UE accounted for 8.7% of our mechanically ventilated patients. The mean APACHE 11 score was 20 (+/- 10), mean time between intubation and UE was 3.1 days (+/- 3.1), mean length of MICU stay was 10.1 days (+/- 10.2) and mean hospital stay was 27.0 days (+/- 36.1). Eighty-seven percent of the UE was deliberate. The rate of reintubation after failed UE was 58.3% of which 71.4% had immediate reintubation. Twenty-nine percent of patients were undergoing weaning during UE. The in-hospital mortality was 25%. All deaths occurred in the group who failed UE. Patients who failed UE had a higher mean APACHE 11 score, a higher mean pre-extubation FiO2 level and a lower mean PaO2/ FiO2 ratio (p < 0.05). CONCLUSION: UE accounted for 8.7% of our mechanically ventilated patients and 58.3% of these patients required reintubation. Failed UE was associated with a higher mortality. A higher APACHE 11 score, higher pre-extubation FiO2 level and a lower PaO2/FiO2 ratio were associated with reintubation after failed UE.

Critical Care↗
PubMed2001

An audit of patients with rheumatic disease requiring medical intensive care.

INTRODUCTION: Medical intensive care for patients with rheumatic disease is usually complicated by significant morbidity and mortality. The aims of this study were to examine the reasons for admission, the outcomes of these patients and the possible prognostic factors in an Asian cohort. MATERIALS AND METHODS: This was a retrospective study of the case records of 29 admissions to the medical intensive care unit (MICU) of Tan Tock Seng Hospital (TTSH) from August 1999 to August 2000. RESULTS: There were 28 patients admitted, of whom 1 had a repeat admission. The majority of these patients were young (mean age 38.9 +/- 16.3 years) and 71.4% were females. Twenty patients (71.4%) had systemic lupus erythematosus (SLE). The main reasons for admission were infection/sepsis syndrome (n = 18), hypotension (n = 16) and acute respiratory failure (n = 14). The observed in-hospital mortality was 64.3%, which was higher than the predicted risk of hospital death of 47.3%. Infection contributed to 55.6% of deaths. The patients who died had a longer mean duration of the rheumatic disease, higher APACHE II scores, higher rates of hypertension and hyperlipidaemia, higher doses of steroid and immunosuppressive therapy and more organ failures. Renal failure and acute respiratory distress syndrome were the two most common organ failures in patients who died. CONCLUSION: Many of our critically-ill patients with rheumatic disease were young females with good functional status. Despite the high mortality, they should be aggressively treated because infection and acute respiratory failure are potentially reversible.

APACHE↗
PubMed2001

Deep vein thrombosis in patients admitted for exacerbation of chronic obstructive pulmonary disease.

INTRODUCTION: There is a lack of data on the prevalence of deep vein thrombosis and pulmonary embolism in patients admitted to hospital for exacerbation of chronic obstructive pulmonary disease. Studies have found that most pulmonary embolism originate from deep vein thrombosis in the lower limbs, thus the prevalence of deep vein thrombosis may give an accurate reflection of the prevalence of pulmonary embolism. The aim of our study was to determine the prevalence of deep vein thrombosis in these patients, using duplex ultrasound of the lower limbs as the screening tool. METHODS: Thirty-three male patients admitted to the general ward for exacerbation of chronic obstructive pulmonary disease were screened for presence of deep vein thrombosis of the lower limbs using duplex ultrasound scan. RESULT: No patient in this study was found to have deep vein thrombosis of the lower limbs. CONCLUSIONS: The prevalence of deep vein thrombosis in local patients admitted for exacerbation of chronic obstructive pulmonary disease is likely to be low. We do not recommend the use of duplex ultrasound to screen for deep vein thrombosis in this group of patients.

Aged↗
PubMed2000

Obstructive sleep apnea syndrome in obese Singapore children.

We set out to determine the prevalence of obstructive sleep apnea syndrome (OSAS) among obese Singapore school children and identify risk factors for OSAS. This study was designed as a prospective study in three phases. Parents completed a questionnaire with regards to sleep and daytime symptoms in Phase 1. Children suspected to have OSAS based on the questionnaire and all with a percent ideal body weight (IBW) >/=180 were called for clinic visits in Phase 2. All whose percent IBW >/=180 and those in whom the physicians strongly suspected OSAS were subjected to a polysomnogram in phase 3. The children were recruited from the School Health Nutritional Clinic for obese children. The investigations were carried out at Tan Tock Seng Hospital. In all, 3,671 children were screened with the questionnaire. Of these, 146 were selected to undergo polysomnography. Twenty-six had abnormal sleep studies with apnea/hypoxia indices (AHIs) >5/hr. The significant clinical feature which correlated with OSAS was sleep sitting up (P = 0.005). The risk is higher in morbidly obese (IBW >/=180), with a prevalence of 13.3% (8/60), than in less obese children (IBW <180). One in eight (12.5%) of these children was asymptomatic and would have been missed based on the questionnaire. Presence of adenotonsillar hypertrophy led to increased risk of OSAS. The prevalence of OSAS was 0.7% (26/3,671) among the obese schoolchildren in Singapore, which is similar to the prevalence reported by others. Using discriminant analysis, the estimated prevalence increased to 5.7%. In the morbidly obese (IBW >/=180), the prevalence rate is higher at 13.3%.

Adenoids↗
PubMed2000

Mid-term clinical and angiographic follow-up outcome after placement of a new balloon expandable stent in native coronary arteries.

The widely disparate characteristics that exist among the different stent designs currently available for clinical use may impact on their acute and late angiographic and clinical results. The BeStent (Medtronic Instent, MN) is a relatively new stainless steel, laser-cut, serpentine stent design with only very limited data regarding its performance. In this report, we examined the results of 74 consecutive patients (54 men, 20 women; mean age, 58 years) treated with 76 BeStents in 75 native coronary arteries with a mean reference size of 2.8 mm. Successful stenting without 30-day major adverse cardiac complications was achieved in 97.3% of procedures, resulting in a significant improvement in diameter stenosis from 85% to 2% (P = 0.0001). Six-month angiographic restudy in 88% of patients revealed a per-lesion in-stent restenosis rate of 27%. At a mean follow-up period of 9.3 months, there were no deaths or myocardial infarctions. In summary, the present study demonstrates that the BeStent has an excellent performance profile, is associated with a low risk of stent thrombosis, and yields an acceptable restenosis rate despite the inclusion of a high proportion of patients with diabetes (41%) and small vessels (< 3.0 mm in diameter; 77%).

Aged↗
PubMed1999

Angiographic restenosis rate in patients with chronic total occlusions and subtotal stenoses after initially successful intracoronary stent placement.

The 5-month angiographic in-stent restenosis rate did not differ between patients with chronic total occlusions (n = 43) and subtotal stenoses (n = 43) equally matched for diabetes status, exact stent design, final expanded stent diameter, stent length, and residual percent diameter stenosis after stent placement; it was 32.5% and 27.9% for those with chronic total occlusions and subtotal stenoses, respectively (p = 0.638). Furthermore, the stent occlusion rate (4.6% vs 6.9%, respectively) was low in both patient groups.

Angioplasty, Balloon, Coronary↗
PubMed1999

Immediate and mid-term results after MultiLink stent implantation in native coronary arteries.

Different stent designs have widely disparate characteristics that may exert a positive or negative impact on their early and mid-term outcomes. The MultiLink stent (Guidant/Advanced Cardiovascular Systems, Santa Clara, CA) is a new coronary stent with only very limited data. In this report, we examined the results of 50 consecutive patients treated with 57 premounted sheathless MultiLink stents in 53 native coronary arteries with reference diameter > or =2.7 mm. Successful stenting was achieved in 98% of patients, resulting in an improvement in diameter stenosis from 91%+/-11% to 1%+/-3% (P = 0.0001). At 1 month, there was no death, myocardial infarction, or stent thrombosis. Angiographic restudy at a mean of 5.0+/-1.8 months in 94% of patients revealed an in-stent restenosis rate of 20.7%. The restenosis rates for diabetic patients (vs. nondiabetic patients), type C lesions (vs. type A/B1 lesions), and the use of 35-mm-long stents (vs. 15-mm-long stents) were 45.4% (14.3%), 56% (< or =11%), and 80% (8.8%), respectively (P < 0.05). In conclusion, the present study demonstrates that the MultiLink stent has an excellent performance profile, is associated with a low risk of stent thrombosis in native coronary vessels, and yields a favorable restenosis rate, particularly after the use of short (15 mm) stents to treat simple lesions.

Aged↗
PubMed1999

A prospective study of infections with atypical pneumonia organisms in acute exacerbations of chronic bronchitis.

The objective of this paper was to study the incidence of 6 atypical pneumonia pathogens or atypical organisms in local patients admitted for acute exacerbation of chronic bronchitis. This is a prospective observational study. Over a period of 3 years (1995 to 1997), 90 patients admitted to a large general hospital in Singapore for acute exacerbation of chronic bronchitis were tested for the following infections: Legionella, Mycoplasma, Chlamydia, influenza A, influenza B and parainfluenza viruses, using paired serological examination. The antibiotic prescribing pattern by the attending physicians in these cases were also examined. Positive serologies were found in 31 patients (34%), of whom 26 patients (28%) had viral infections. The most common organism was influenza A with 18 positive serologies (20%). Five patients were tested positive for Legionella. There was no evidence of acute infections by Mycoplasma pneumoniae or chlamydia using serological tests.

Acute Disease↗
PubMed1998

Early experience with the NIR intracoronary stent.

Immediate and midterm results of 61 NIR stent placement attempts in 55 native coronary vessels in 52 patients demonstrate a high clinical success rate of 98%, no early stent thrombosis, and a 5-month angiographic restenosis rate of 23%. The frequency of in-stent restenosis was significantly heightened in small vessel sizes and in diabetic patients.

Angioplasty, Balloon, Coronary↗
PubMed1998

Midterm angiographic outcome of single-vessel intracoronary stent placement in diabetic versus nondiabetic patients: a matched comparative study.

BACKGROUND: It remains controversial whether diabetes is associated with an increased risk of restenosis after intracoronary stenting. METHODS AND RESULTS: We selected 42 diabetic patients and an equal number of nondiabetic patients with follow-up angiographic restudy after single-vessel stenting, matched for 4 important stent-related and angiographic variables (stent design, reference vessel size and expanded stent diameter, coronary vessel treated, and poststent residual diameter stenosis). The 2 patient groups did not differ in their baseline lesion severity and acute luminal gain. At 5-month angiographic assessment, the observed in-stent restenosis rate was significantly higher in diabetic than nondiabetic patients (40.5% vs 16.7%, P = 0.0157). It was highest in diabetic patients who received small stents <3.0 mm in diameter and intermediate in diabetic patients who received larger stent sizes (55% vs 27%, P = 0.0675). The frequency of restenosis in nondiabetic patients, however, was low; it was 18% and 15% in those who received small stents and larger stents, respectively (P = 0.7823). CONCLUSIONS: Our data suggest that diabetes predisposes to an increased risk of in-stent restenosis, particularly in small vessels.

Coronary Angiography↗
PubMed1997

Safety and efficacy of angiography-guided stent placement in small native coronary arteries of < 3.0 mm in diameter.

BACKGROUND AND HYPOTHESIS: Increased operator experience, greater insight in stent deployment techniques, and improved poststent medication regimen have significantly reduced the risk of thrombotic stent closure following stent placement in large coronary arteries (> or = 3.0 mm in diameter). Whether equally favorable results are afforded by stent placement in small vessels (< 3.0 mm), however, remains unclear. Accordingly, the aim of this study was the specific examination of the risk of stent placement in small native coronary vessels, using stent deployment technique consisting of supplementary dilatations with larger balloons or high-pressure inflations, and aggressive aspirin-ticlopidine and short-term oral anticoagulation poststent therapy. METHODS: Forty-seven balloon-expandable stents (20 Gianturco-Roubin, 21 NIR, 6 Palmaz-Schatz) were successfully implanted without intravascular guidance in 45 native coronary arteries (mean reference diameter of 2.5 mm) in 44 consecutive patients (31 men, 13 men), the majority of whom (87%) were stented for the treatment of failed or suboptimal balloon angioplasty outcome. RESULTS: Successful stent placement reduced the lesion diameter stenosis from 91 +/- 9% to 3 +/- 7% (p = 0.0001). There were no early stent thrombosis or major cardiovascular events prior to hospital discharge. During a 12-month follow-up period, most patients remained symptomatically improved and no myocardial infarction, stroke, or death was observed. Five-month angiographic reassessment revealed an in-stent restenosis rate of 41%, which was higher in vessels < or = 2.5 mm in size (47 vs. 33% for vessels > 2.5 mm, p = 0.2747). CONCLUSIONS: In selected patients with small native coronary vessels < 3.0 mm in diameter, angiography-guided optimal stent placement is associated with a low risk of stent thrombosis and bleeding complications. However, the in-stent restenosis rate is high with the stents used in this study.

Angioplasty, Balloon, Coronary↗
PubMed1997

Maximal respiratory pressures in adult Chinese, Malays and Indians.

Maximal static inspiratory and expiratory mouth pressures (PI,max and PE,max, respectively) enable the noninvasive measurement of global respiratory muscle strength. The aim of this study was primarily to obtain normal values of PI,max and PE,max for adult Chinese, Malays and Indians and, secondarily, to study their effect on lung volumes in these subjects. Four hundred and fifty two healthy subjects (221 Chinese, 111 Malays, 120 Indians) were recruited. Measurements of PI,max from residual volume (RV), PE,max from total lung capacity (TLC) and forced vital capacity (FVC) were obtained in the seated position. There were significant ethnic differences in PI,max and PE,max measurements obtained in males, and FVC measurements in both males and females. Chinese males had higher PI,max values (mean (+/-SD) 88.7+/-32.5 cmH2O) and higher PE,max values (113.4+/-41.5) than Malay males (PI,max 74.0+/-22.7 cmH2O, PE,max 94.7+/-23.4 cmH2O). Chinese males had higher PE,max than Indian males (PI,max = 83.7+/-30.0 cmH2O, PE,max 98.4+/-29.2 cmH2O). There were no significant differences among Chinese females (PI,max 53.6+/-2.3 cmH2O, PE,max 68.3+/-24.0 cmH2O), Malay females (PI,max 50.7+/-18.3 cmH2O, PE,max 63.6+/-21.6 cmH2O) and Indian females (PI,max 50.0+/-15.2 cmH2O, PE,max 60.7+/-20.4 cmH2O). In both sexes, the Chinese had a higher FVC compared with Malays and Indians. After adjusting for age, height and weight, race was still a determinant for PE,max in males, and FVC in both sexes. The FVC only correlated weakly with PI,max and PE,max in both sexes. Ethnic differences in respiratory muscle strength, and lung volumes, occur among Asians. However, respiratory muscle strength does not explain the differences in lung volumes in healthy Asian subjects.

Adult↗
PubMed1997

Percutaneous transluminal coronary angioplasty in Singapore General Hospital in 1995: a medical audit.

BACKGROUND: There are few reports which describe the outcomes of unselected groups of patients undergoing percutaneous transluminal coronary angioplasty (PTCA) locally. This study has undertaken to audit the outcome of patients undergoing elective PTCA at Singapore General Hospital. METHODS: Procedural data and acute outcomes were recorded prospectively in all patients undergoing PTCA over a 12 month period. A retrospective casenotes review of all patients were carried by independent observers to determine out-of-lab complications. RESULTS: Seven hundred and eight-two patients underwent PTCA in 1995. Acute angiographic success rate was 90.9% and early clinical success rate was 89% ie excluding death, coronary bypass surgery and non fatal myocardial infarction. There were only two deaths in the series (0.26%). CONCLUSION: The audit confirms the importance of a high volume PTCA cases to achieve excellent results. The data serve as a useful background for future comparison of outcomes.

Aged↗
PubMed1996

Percutaneous balloon mitral valvuloplasty in patients with mitral restenosis after previous surgical commissurotomy. A matched comparative study.

BACKGROUND: Although the efficacy of percutaneous balloon mitral valvuloplasty in patients with unoperated mitral stenosis has been well documented, there exists less clear-cut data on its effectiveness in patients with mitral restenosis after previous surgical commissurotomy. Accordingly, the purpose of this study was to evaluate our immediate and midterm results of balloon mitral valvuloplasty in this subset of patients with previous mitral surgery. METHODS: Between October 1991 and August 1995, 29 consecutive patients with mitral restenosis after prior surgical commissurotomy (group 1) underwent Inoue balloon mitral valvuloplasty. They were matched on a patient-to-patient basis with regard to baseline mitral echocardiographic score mitral valve area, severity of angiographic mitral regurgitation and follow-up duration with 29 other patients with unoperated mitral stenosis (group 2) who underwent balloon mitral valvuloplasty during the same study period. RESULTS: Balloon mitral valvuloplasty yielded identical improvements in transmitral gradient and mitral valve area (from 0.8 to 1.6 cm2) determined echocardiographically, and similar changes in the severity of mitral regurgitation in both groups of patients. All procedures were successfully completed without major cardiac complications. Follow-up echocardiographic assessment in 73% of patients revealed equal mitral valve area (1.6 cm2) and a restenosis rate of 17%, with no difference in the restenosis rate between the two groups. CONCLUSION: Balloon mitral valvuloplasty in selected patients with mitral restenosis after past surgical commissurotomy can be performed safely and with similar immediate and midterm efficacy as in patients with de novo mitral stenosis.

Adult↗
PubMed1996

Percutaneous Inoue-Balloon Mitral Commissurotomy in Patients with Coexisting Moderate Mitral Regurgitation, and Severe Subvalvular Disease and/or Mitral Calcification.

The present study examined the safety and immediate and late outcome of 12 patients with coexisting moderate (angiographic grade 2+) mitral regurgitation and significant subvalvular disease and/or calcified mitral valves (group 1) after percutaneous balloon mitral commissurotomy (BMC) and compared the results with 64 patients without these adverse valve features (group 2). BMC produced a significantly smaller echocardiographically determined mitral valve area improvement in group 1 compared with group 2 (from 0.7 +/- 0.2 cm2 to 1.3 +/- 0.3 cm2 vs. 0.8 +/- 0.2 cm2 to 1.7 +/- 0.4 cm2, respectively, p < 0.05). Similarly, compared with group 2, less patients in group 1 obtained an optimal valvuloplasty outcome defined as a ³ 50% increase in mitral valve area or a final valve area of ³ 1.5 cm2 without final ³ 3 grade angiographic mitral regurgitation (75% vs. 95%, p < 0.05). There was, however, no severe (³ angiographic grade 3+) mitral regurgitation in group 1 compared with 1 in group 2 (p = NS). At a mean follow-up of 19 +/- 14 months, there were no deaths or strokes. Restenosis was noted in 4 patients; 3 in group 1, and 1 in group 2. We conclude that BMC is safe and effective in patients with pre-existing moderate mitral regurgitation and severe subvalvular disease and/or significant mitral calcification with minimal risk of creating severe mitral regurgitation. The valve area improvement was, however, substantially smaller and the restenosis rate higher than those without moderate mitral regurgitation and favorable valve anatomy.

Journal Article↗