Proceedings of Singapore Healthcare

Volume 20 Number 4 2011
Cardiovascular and Respiratory Medicine

EDITORIAL
Tackling the Burden of Cardiovascular and Respiratory Disease in Singapore
Liew R


ORIGINAL ARTICLE
Combined Bipolar/Unipolar Radiofrequency Maze is Superior to Unipolar Maze in Concomitant Surgery
Chua YL, Soon JL, Masakazu N, Lim SL

Abstract
Introduction: Atrial fibrillation is the most common arrhythmia with significant morbidity and mortality. Radiofrequency (RF) ablation, despite its shortcomings, remain an acceptable and ‘simple’ technique.

Methods: We reviewed 137 consecutive concomitant irrigated RF modified maze procedures, and compared the outcomes of 65 patients undergoing Unipolar-RF versus 72 patients using the combined Uni/Bipolar-RF approach. All patients were prospectively followed clinically, with serial electrocardiography and selective echocardiography. One hundred and twenty-two patients (89.1%) underwent mitral valve procedures, and eight coronary bypass, and seven adult congenital operations were performed.

Results: The predominantly male (54.7%) patients had a mean age of 58.3±11.5 years (23-88 years). At median follow-up of 3.21 years (0.01-6.06 years), 15 (10.9%) patients were lost to follow-up. Freedom from AF in the Uni/Bipolar-RF group was higher at six months: 85.1% (57/67) versus 65% (39/60) in the Unipolar-RF group (P=0.012). This superior trend persisted at five years: 100% (5/5) in the Uni/Bipolar-RF group versus 79.5% (31/39) in the Unipolar-RF group, although this is not statistically significantly (P=0.566). Patients with left atrial dilatation beyond 7.6cm were more likely to remain in AF (OR 0.44, 95% CI, 0.19-1.00, P=0.049). Perioperative mortality was 2.9%. There was no collateral damage by the device and procedure. The mean survival for patients AF-free at last follow-up is 5.73 years (95% CI, 5.48-5.98), comparable to 5.58 years (95% CI, 5.07-6.10) in those remaining in AF. Thirty (22.6%) patients were completely off anti-arrhythmic medication while 36 (25.6%) were anticoagulant-free.

Conclusion: The combined Uni/bipolar-RF modified bi-atrial Maze technique is simple, safe and superior to isolated Unipolar-RF ablation. Midterm results continue to support its use although long-term durability remains to be elucidated.
Keywords:Atrial fibrillation, Arrhythmia surgery, Mitral valve

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REVIEW
Screening for Coronary Artery Disease using CT Coronary Angiography, Coronary Artery Calcium Scoring and Myocardial Perfusion Imaging: A Review of Current Evidence of Potential Benefits and Risks
Wong SS, Keng FYJ

Abstract
Screening for coronary artery disease (CAD), using CT coronary angiography, coronary artery calcium scoring and myocardial perfusion imaging, seems an attractive idea. However, there is considerable uncertainty whether the overall potential benefits outweigh the risks. In a situation where the prevalence of disease is very low, the positive predictive value of any test will tend to be low, and false positive results frequent, requiring a large number of individuals to undergo further testing to confirm disease in a small number of patients. Even when disease is detected, the benefits of revascularisation are uncertain in asymptomatic populations. There is considerable uncertainty about the risks from radiation as a result of imaging tests such as CT scans. Based on available data, the actual risks of malignancy for most individuals appear to be small and of limited concern in a symptomatic patient with a moderate likelihood of disease. However, in a low risk population as in the context of coronary artery screening, the likelihood of benefit is likely to be much smaller due to the lower likelihood of disease, and may well be balanced by the possibility of harm. Screening for CAD using CT coronary angiography, coronary artery calcium scoring and myocardial perfusion imaging should be undertaken only after all these limitations have been properly discussed with the patient, and the patient’s global risk of CAD has been estimated using conventional risk scoring. Testing should not be undertaken without careful consideration of whether the test result might change the patient’s risk category and plan of management.
Keywords: Computed tomography coronary artery angiography, Coronary artery calcium scoring, Myocardial perfusion imaging, Radiation.

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Review on Non-invasive Risk Stratification of Sudden Cardiac Death
Fam JM, Ching CK

Abstract
Sudden cardiac death (SCD) is one of the most significant and challenging problems facing modern medicine today given its unpredictable nature. The evaluation of the patient at risk for sudden cardiac death still remains a complex task. The use of ICDs (implantable cardioverter defibrillators) remains the mainstay of primary prevention of sudden cardiac death. However, much remains to be determined on how best to identify patients at high risk of sudden cardiac death who would most benefit from ICD implantations. This paper will review the current issues in the risk assessment of sudden cardiac death and non-invasive markers of sudden death.
Keywords: Risk stratification, Sudden death

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Medical Therapy for Obstructive Sleep Apnoea
Ong TH

Abstract
Obstructive Sleep Apnoea (OSA) is increasingly recognised as a condition that not only causes excessive daytime sleepiness, but is also an important cardiovascular risk factor. Treatment of OSA should include conservative measures such as weight loss and positional therapy, the nuances of which are discussed in this article. However this in itself is not sufficient treatment for most patients. The first line of treatment for OSA that is recommended across the entire spectrum of disease is continuous positive airway pressure (CPAP) therapy. Indications for initiating CPAP are discussed, as well as possible alternatives to CPAP such as surgery or dental devices. In initiating CPAP treatment, machine-patient interface needs to be carefully considered, as there is a wide range of masks available. Factors to be considered in the choice of CPAP machine and mode are discussed. Finally, patient-specific factors such as patient acceptance of treatment, common problems encountered in CPAP follow-up and the importance of patient education are addressed.
Keywords: Conservative measures, Continuous positive airway pressure, Obstructive sleep apnoea

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Neutrophil Gelatinase Associated Lipocalin: An Emerging Biomarker for Acute Kidney Injury in Cardiovascular Disease
Yeo C, Khurana R

Abstract
Acute kidney injury (AKI) commonly occurs in hospitalised patients resulting in short and long-term morbidity and mortality. A subset of patients especially those with cardiovascular diseases appear particularly vulnerable. The diagnosis of AKI currently depends on changes in serum creatinine and is usually made at least 24 to 48 hours after the initial renal insult. This hinders formulation of possible early therapeutic strategies which could otherwise reduce the clinical sequelae of AKI. Neutrophil gelatinase-associated lipocalin (NGAL) is released in both serum and urine, and has shown great promise in identifying AKI as early as two to four hours after renal injury. NGAL has been demonstrated to be both specific and sensitive in a variety of renal conditions associated with AKI, compared to serum creatinine. This article discusses the emerging role of NGAL in the diagnostic and prognostic evaluation of AKI secondary to cardiovascular diseases and interventions including its benefits and pitfalls. NGAL has been shown to be useful in the diagnosis of AKI particularly for contrast induced nephropathy (CIN) after percutaneous coronary intervention (PCI) and renal dysfunction complicating acute and chronic heart failure. Larger prospective outcome studies with therapeutic interventions are warranted to further validate the role of NGAL in the diagnosis of AKI and in cardiorenal syndrome.
Keywords: Acute kidney injury, Heart failure, Ischaemic heart disease, NGAL, Percutaneous coronary intervention

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CASE REPORT
Managing Cardiovascular Incidents in the Intra-operative Magnetic Resonance Imaging (iMRI) Environment: Lessons from Three Case Studies
Zheng JX, Tan TK

Abstract
In recent years, the use of magnetic resonance imaging (MRI) has extended into the operating theatre, especially in the field of neurosurgery. By providing real-time images during surgery, intra-operative MRI (iMRI) facilitates safer and more complete brain tumour resection. However, the iMRI environment poses additional challenges to the anaesthetist when managing intra-operative cardiovascular events. Through three case examples, this article will discuss the issues of cardiovascular resuscitation, cardiac pacing and cardiovascular monitoring in the iMRI environment.
Keywords: Anaesthesia, Cardiovascular incidents, Intra-operative, Magnetic resonance imaging, Neuroanaesthesia

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A Pleural Effusion with an Unusual Cause
Tan AH, Ong TH, Takano A

Abstract
A 35-year-old presented with an incidental finding of a small left pleural effusion on a routine chest radiograph. A diagnostic pleurocentesis revealed a chylous effusion. CT showed a small left pleural effusion, multiple small pulmonary nodules and thickened interstitial lines in the right lung. Video-assisted thoracoscopic biopsy of the right lung revealed features consistent with diffuse pulmonary lymphangiomatosis.
Keywords: hylothorax, Lung/pathology, Lung/radiography

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Case of Idiopathic Left Ventricular Tachycardia (ILVT)
Hamid N, Chia S

Abstract
Introduction: The objective of this case report is to illustrate a case of idiopathic left ventricular tachycardia (ILVT). It is important to distinguish key features to differentiate ILVT from other types of ventricular tachycardias.

Clinical picture: A 33-year-old male presented with palpitations. Clinical examination was unremarkable, except a heart rate of 170 beats/min. ECG showed a right bundle branch morphology, left superior frontal plane and a relatively narrow QRS duration. A diagnosis of ILVT was made.

Treatment: Intravenous verapamil was given and the ILVT was terminated.

Conclusion: ILVT differs from other types of VT, such as right ventricular outflow tract (RVOT), in terms of mechanisms, site of origin and management. Overall, ILVT has a good prognosis, compared to VTs seen in ischaemic cardiomyopathy.
Keywords: Idiopathic, Tachycardia, Ventricular

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LABORATORY INSIGHTS
Clinical Use of Natriuretic Peptides
Yap CYF, Phua SK, Aw TC

Abstract
Either B-type natriuretic peptide (BNP) or NT-proBNP may be used as a diagnostic, screening, prognostic and therapeutic tool for CHF. The Food and Drug Administration (FDA) cleared the cut-off point for BNP at 100 pg/mL, and that of NT-proBNP at 125 pg/mL for patients <75 years and 450 pg/mL for those >75. A steadily rising titre even below the cut-off value should be raised as a concern as heart failure is progressive if left untreated and may result in cardiac death. Both biomarkers are also featured in lab investigations for patients with acute coronary syndrome (ACS).
Keywords: Acute heart failure, B-type natriuretic peptide, Congestive heart failure, Dyspnea, N-terminal-proBNP

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STATISTICS
Measures of Diagnostic Accuracy: Sensitivity, Specificity, PPV and NPV
Wong HB, Lim GH