Robotic navigation set to guide arrhythmia treatment in SE Asia

Medical Tribune October 2009 P4
David Brill

Cardiac arrhythmia patients can be treated faster, more safely and with less radiation exposure, following the unveiling of a cutting-edge robotic system at the National Heart Centre Singapore (NHCS).

The technology allows electrophysiological catheter ablation to be done by remote control, using magnets to guide the catheter to its target with dexterity that cannot be achieved by hand.

Cardiologists direct proceedings from a computer workstation – sparing them from neck and back pain that can result from manual ablation procedures, which last up to 6 hours. Procedural time is expected to drop to 2-3 hours with the magnetic navigation system.

Twelve patients have already been treated with the system, which is the first of its kind in Southeast Asia.

“The robotic magnetic navigation system can allow us to safely map the heart to 1 to 2 mm accuracy and precision without the use of fluoroscopy,” said Dr. Teo Wee Siong, director of electrophysiology and pacing and senior consultant cardiologist at NHCS.

“This precision cannot be achieved by conventional ablation with our hands manually, no matter how skilled we are. This will definitely improve patient outcome and safety, especially in complex arrhythmia cases such as atrial fibrillation and ventricular tachycardia,” he said.

The procedure eliminates physician radiation exposure and lowers patient exposure by 40 percent compared with conventional ablation. The new catheters are also softer and more flexible than manually operated versions, thereby reducing the risk of damaging the heart walls from 2-3 percent to less than 1 percent.

The feasibility of magnetic navigation systems for catheter ablation was first demonstrated 7 years ago in dogs and pigs. [Circulation 2002;106:2980] The intervening years have seen the technology evolve and progress to human usage, with centers in the US, Italy and Germany among the first to report their results. Some procedural times were initially longer than conventional ablation, but have shortened with growing experience.

Most recently, the Texas Cardiac Arrhythmia Institute, US, reported success in 164 of 193 robotic catheter ablations (85 percent), compared to 159 of 197 manual ablations (81 percent). Mean exposure to fluoroscopy was slightly increased for the first 50 procedures performed with the robotic system (61.8 minutes versus 58.4 minutes for conventional ablation), but dropped to 44.5 minutes over subsequent procedures. [J Cardiovasc Electrophysiol 2009 Jul 28; Epub ahead of print]

NHCS sees around 300 patients each year requiring catheter ablation and an implantable cardioverter-defibrillator. It estimates that around 60 percent of cases could be treated with the new magnetic navigation system.

Aspirin ineffective for primary CVD prevention

Medical Tribune October 2009 P6

David Brill

Aspirin should not be used routinely for primary prevention of cardiovascular disease in people with asymptomatic atherosclerosis, results of a randomized trial suggest.

The Aspirin for Asymptomatic Atherosclerosis (AAA) study found that daily aspirin (100mg) did not significantly reduce vascular events compared to placebo, but increased rates of hemorrhage and gastrointestinal complications.

The trial involved 3,350 Scottish men and women aged 50 to 75 who had a low ankle brachial index (ABI; ≤ 0.95) – indicative of peripheral atherosclerosis. They were followed up for a mean of 8.2 years for primary outcomes of coronary events, stroke and revascularization.

A total of 357 study subjects experienced a vascular event: 181 in the aspirin group and 176 in the placebo group (hazard ratio 1.03, 95% CI 0.84 – 1.27). Secondary outcomes, including angina, transient ischemic attack and all-cause mortality, were also not significantly different between groups.

“There is no support for the routine use of aspirin for the prevention of vascular events in the context of ABI screening in the general population,” said study investigator Professor Gerald Fowkes of the University of Edinburgh, UK.

“It is possible that in the general population, aspirin could produce a smaller reduction in vascular events than this trial was powered to detect, but it is questionable whether such an effect, together with aspirin related morbidity, would justify the additional resources and health care requirements of an ABI screening program,” he said.

Fowkes noted that compliance is lower in the primary prevention setting, adding: “Whether aspirin is beneficial in clinical practice in a patient with a low ABI who was fully compliant with the medication is unknown, so our results cannot be extrapolated into that situation.”

Thirty four major hemorrhages occurred in the aspirin group and 20 in the placebo group (2 percent versus 1.2 percent; hazard ratio 1.71; 95% CI 0.99 – 2.97). There were 14 and eight cases, respectively, of gastrointestinal ulcers (0.8 versus 0.5 percent).

The efficacy of aspirin is well established for secondary prevention in patients with a history of cardiovascular disease, but the risk-benefit ratio for primary prevention in low-risk individuals remains less clear. A recent meta-analysis of six primary prevention trials found that aspirin reduced rates of serious vascular events by 12 percent, but increased major gastrointestinal and extracranial bleeds. [Lancet 2009;373:1849-60]

Recent studies have also questioned the use of aspirin for primary prevention in diabetic patients – a common practice which is advocated in international guidelines. [BMJ 2008;337:a1840]

New biomarker tests could slash heart attack diagnosis time

Medical Tribune October 2009 P7
David Brill

New-generation tests can rapidly accelerate the diagnosis of acute myocardial infarction (MI) – saving time, improving convenience and reducing costs in the emergency department, studies show.

High-sensitivity cardiac troponin assays can now rule MI in or out in patients presenting within the first hours of chest pain onset, thereby removing the delays associated with conventional tests and allowing for earlier transfer and treatment.

Testing for stress marker copeptin, meanwhile, can exclude MI with 99 percent certainty, thus saving many patients from unnecessary further testing.

Professor Christian Müller, reviewing the data, said that the new tests could answer an unmet clinical need in the assessment of chest pain, since current troponin tests have an undetectable “blind interval” of 3-4 hours after the onset of MI. Even if patients follow recommendations and present within 2 hours of chest pain, the test will be negative and electrocardiography monitoring will be required for 6 to 8 hours.

“The current-generation troponin tests are important but have important limitations in [making an] early diagnosis. There seem to be two approaches to solve this problem: either use troponin in combination with copeptin, or perhaps the approach now favored by many is the use of sensitive troponin assays,” said Müller, of the University Hospital Basel, Switzerland.

The new troponin assays were tested in two European multicenter trials, published recently in the New England Journal of Medicine. [2009;361:858-67; 2009;361:868-77]

German investigators tested 1,818 consecutive patients at admission and 3 and 6 hours later. Diagnostic accuracy at admission was higher with a sensitive troponin I test, as compared to a conventional troponin T test (area under the receiver-operated-characteristic curve [AUC] 0.96 versus 0.85). The new test had a clinical sensitivity of 90.7 percent and specificity of 90.2 percent, with accuracy unaffected by the time of chest pain onset.

The second study, led by Müller and colleagues, involved 718 consecutive patients – 123 of whom were ultimately diagnosed with acute MI. Four high-sensitivity assays were tested: all were superior to a conventional test (AUCs 0.95 – 0.96 versus 0.90) when performed at presentation. The difference was most marked in patients presenting within 3 hours of chest pain onset (AUCs 0.92 – 0.94 versus 0.76).

In an earlier study, Müller and colleagues tested 487 potential MI patients for copeptin, the C-terminal section of the vasopressin prohormone, which denotes endogenous stress. Combination with a conventional troponin T test yielded an AUC of 0.97, compared to 0.86 for the troponin test alone (P<0.001). Low levels of both copeptin (<14 pmol/l) and troponin T (≤0.01 μg/l) correctly excluded MI in the majority of cases (sensitivity 98.8 percent; negative predictive value 99.7 percent). [J Am Coll Cardiol 2009;54:60-8]

ESC offers guidance on syncope workup

Medical Tribune October 2009 P9

David Brill

The European Society of Cardiology has updated its guidelines to facilitate the diagnosis and management of syncope – a common clinical challenge for GPs and specialists alike.

A novel diagnostic workflow promotes early risk stratification – enabling prompt treatment for those who need it and avoiding unnecessary therapy for those who don’t.

New emphasis is also placed on prolonged monitoring for patients with benign but recurrent syncope, which can adversely affect quality of life.

The guidelines reflect a multidisciplinary collaboration and have been endorsed by leading European and American societies, ranging from emergency medicine to geriatrics and neurology.

The authors recommend that initial evaluation be performed to divide patients into syncope or non-syncopal loss of consciousness. Genuine cases of syncope should then be divided into certain and uncertain diagnosis – with risk stratification performed for the latter.

“In the vast majority of the population the cause of syncope is something very benign and it has no consequences for the patient. But in some, syncope can be the herald of a severe cardiac arrhythmia or even the first manifestation of a future sudden death, so it is important to recognize in which patients it is severe and in which patients it is benign,” said task force chairman Professor Angel Moya, of the University Hospital Vall d’Hebron in Barcelona, Spain.

The authors have also revised the definition of syncope itself, such that reduced cerebral blood flow is now a prerequisite for diagnosis. They define syncope as: “a transient loss of consciousness due to transient global cerebral hypoperfusion characterized by rapid onset, short duration and spontaneous complete recovery.”

“Without this diagnostic addition the definition of syncope becomes wide enough to include other disorders such as epileptic seizures and concussion. In fact [it] would be nothing more than ‘loss of consciousness,’ irrespective of mechanism and duration,” said Moya.

Syncope is a common problem, thought to affect up to 50 percent of people at least once in their lifetime. The three most common types identified in the guidelines are reflex syncope, orthostatic hypotension and cardiac syncope.

Reflex syncope results from an alteration of the cardiovascular reflexes that control circulation, leading to hypotension and reduced cerebral blood flow. Orthostatic hypertension is typically a recurring event resulting from circulatory abnormalities, which may also cause other symptoms such as dizziness and palpitations. Cardiac syncope is more serious, and is usually a sign of an underlying arrhythmia which should be treated.

The new guidelines – developed in collaboration with the European Heart Rhythm Association, the Heart Failure Association and the Heart Rhythm Society – were published online in the European Heart Journal. [2009 Aug 27; Epub ahead of print]

Experts back healthy lifestyle in battle against CVD

Medical Tribune October 2009 SFV
David Brill

The drive to promote healthy living is gathering fresh momentum, with the publication of two major new studies suggesting substantial potential to tackle cardiovascular disease at a population-wide level.

Fourteen-year follow-up of over 83,000 healthy women in the Nurses’ Health Study showed that those who ate well, exercised and had lower BMI were considerably less likely to develop hypertension – the leading preventable contributor to death in women.

The Physicians’ Health Study, meanwhile, reported that keeping healthy significantly reduced the risk of developing heart failure over 22 years in a cohort of some 21,000 men. Those who followed at least four out of six healthy habits had a 10.1 percent lifetime risk of developing heart failure, compared to 21.2 percent for men who followed none of the six.

Both Asian and international experts are calling for a renewed focus on public health promotion in light of the data.

Dr. Goh Ping Ping, medical director of the Singapore Heart Foundation and chief of cardiology at Changi General Hospital, said that a lot of work remains to be done at the community level and urged doctors to “take a very proactive role”, particularly with opportunistic screening.

“Even if a patient comes in for a medical problem that is not directly related to the heart or to hypertension, [doctors] could also take the opportunity to check their blood pressure, or educate them on these very simple lifestyle principles,” she said, adding that further educational materials should be kept on hand for such cases.

An editorial accompanying the two papers noted that the “powerful simplicity” of the message begs a rethink on the very concept of lifestyle, which is often perceived to be an individual choice. Rather, it is an interaction between personal and societal factors that defines the approach to cardiovascular disease prevention, according to Dr. Véronique Roger of the Mayo Clinic, Minnesota, US. [JAMA 2009;302:437-439]

“The studies … underscore that healthy lifestyle will help prevent cardiovascular disease and greatly enhance health, which is a compelling reminder that health is the shared responsibility of individuals and communities. This in turn implies that public health policies and clinical care must join forces to achieve effective disease prevention,” she wrote.

The Nurses’ Health Study enrolled 83,882 women aged 27 to 44 in 1991, and followed them up until 2005. [JAMA 2009;302:401-11]

BMI, exercise, alcohol intake, adherence to the Dietary Approaches to Stop Hypertension (DASH) diet, use of non-narcotic analgesics and folic acid supplementation were all independently associated to risk of developing hypertension. Women who scored well on all six factors had a hazard ratio of just 0.22 (95% CI 0.10 – 0.51) for incident hypertension. Such healthy livers, however, comprised just 0.3 percent of the population.

The Physicians’ Health Study involved 20,900 men with a mean age of 53.6 at enrollment in 1982, with follow-up until 2008 (mean 22.4 years). [JAMA 2009;302:394-400]

Six lifestyle factors were also assessed: smoking, exercise, body weight, alcohol intake, consumption of fruits and vegetables, and consumption of breakfast cereals. Again, all factors were independently and jointly linked to an increased risk of heart failure.

Singapore’s Health Promotion Board welcomed the studies as “good evidence as to the importance of a healthy lifestyle,” given their size and robust data.

“A large proportion of chronic disease amongst the Asian population can be attributed to lifestyles, i.e. eating habits and lack of physical activity,” said Dr. Shyamala Thilagaratnam, director of the Healthy Ageing Division. “Therefore encouraging Singaporeans to lead a healthy lifestyle is likely to be useful in reducing the burden of chronic disease. Singaporean and other Southeast Asian doctors should use this as good evidence to promote the adoption of a healthy lifestyle amongst their patients.”

Goh added that it is important to adapt the messages of the studies to match local cultures and habits.

“Our dietary patterns are quite different – they talk about cereals for breakfast but that probably doesn’t apply too well here. It’s probably more about telling people not to have nasi lemak or roti prata, for example, and to substitute with something else,” she said.

Jury still out on clinical exams for breast cancer screening

Medical Tribune October 2009 P12

David Brill

Controversy looks set to continue over the benefits of clinical breast examination (CBE) for cancer screening, following the publication of a large population-based study which could raise as many questions as answers.

Results from the Ontario Breast Screening Program show that adding CBE to mammography improves cancer detection rates, but considerably increases the number of false-positive results.

For every 10,000 women screened, the addition of CBE would detect four more cancers but expose 219 women to unnecessary further testing – along with its extra risks, costs and anxiety.

This risk-benefit ratio must be weighed up carefully, and women should be fully informed before consenting to CBE, wrote the researchers, led by Dr. Anna Chiarelli of Cancer Care Ontario, Toronto Canada. [J Natl Cancer Inst 2009 Aug 31; Epub ahead of print]

They screened 290,230 women aged 50 to 69 between 2002 and 2003, and followed them up for 12 months. Of these women, 232,515 received mammography plus CBE at 68 centers (nine regional and 59 affiliated), whereas 57,715 received mammography alone at 34 affiliated centers.

US experts called it “a steep price” for adding CBE to mammography but reserved judgment on how the findings should influence practice, concluding in an editorial that “more answers are needed on the role of CBE in breast cancer screening before definitive recommendations for or against its use can be made.”

“While we wait for those answers, the data presented by Chiarelli et al. suggest that CBE must be done well if it is to be done at all, with the acknowledgment that overall referrals and false-positive results will increase,” wrote Drs. Mary Barton and Joann Elmore, of the Agency for Healthcare Research and Quality, Rockville, and the University of Washington School of Medicine, Seattle, respectively. [J Natl Cancer Inst 2009 Aug 31; Epub ahead of print]

Barton and Elmore also called for the creation of universal standards for CBE, noting that inconsistency in the duration of examinations and the search pattern used can affect the accuracy of the test. They note that the highest-volume centers in the Ontario study also had the highest sensitivities and lowest false-positive rates – an observation which supports their case for standardization.

CBE has been advocated in some quarters since it can detect cancers which are missed by mammography – the gold standard for breast cancer screening. It has yet to be demonstrated conclusively, however, that addition of CBE to screening actually reduces mortality.

The practice is common in the US: one report found that 18 percent of screening centers surveyed performed CBE routinely alongside mammography, while another study found that 65 percent of women reported having CBE in the preceding 2 years. [Open Clin Cancer J 2008;2:32-43; AJR Am J Roentgenol 2005;184:433-8]

Breast cancer was traditionally less common in Asia than the West but rates are rising rapidly. In Singapore, the only Asian country with a national breast cancer screening program, it is now the number one cancer among women. The incidence rose 2.5-fold between 1968 and 2002, according to data from the national cancer registry.

First-line screening in the BreastScreen Singapore program is with mammography alone. CBE is included among possible follow-up tests, along with ultrasound, repeat mammography and biopsy.

Breast cancer has also become the leading cancer among women in Hong Kong – responsible for 21 percent of cancer cases in 2002. A self-referral, opportunistic mammography screening program at the Tung Wah Group of hospitals was shown to improve early detection and prognosis after 46,637 mammograms, with comparable results to Western programs. Screening was well received by the community, and the model has been proposed as a basis for a national program. [Hong Kong Med J 2007;13:106-13c]

Surveys in both Singapore and Hong Kong have shown, however, that public knowledge about breast cancer and screening is low, and myths and misconceptions are common. Only 57 percent of Singaporean women aged 40 and above had gone for a screening mammogram, while 58 percent of Hong Kong women had never even heard of mammographic screening. [Singapore Med J 2009;50:132-8; Breast J 2005;11:52-6]