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Monday, May 5, 2014 C7

HEALTH LAB REPORT ............................................ Jeanette Wang jeanette.wang@scmp.com

SHOCK OF

THE NEW Latest defibrillator can be implanted without putting electrodes into the heart, writes Jeanette Wang

The S-ICD system is placed under the skin of the chest wall, over the ribs and sternum. Illustration: Boston Scientific

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along the left side of the breast new defibrillator bone. The surgery for that detects implanting the device takes arrhythmias and around an hour, compared to shocks the heart up to two hours for a back into normal conventional device, thereby rhythm – yet has no wires that reducing the time a patient is touch the heart – has been anaesthetised. successfully implanted in two Apart from a highly patients in Hong Kong, the first significant reduction in the in Asia. A team from the University of risk of developing severe Hong Kong’s Li Ka Shing Faculty complications, the S-ICD can also be placed solely by of Medicine performed the anatomical landmarks without surgeries and both patients are using X-ray, hence reducing making satisfactory progress in patients’ radiation exposure. rehabilitation. Further, replacing worn-out “The greatest advantage of electrodes in the new device the new defibrillator is that the needs only a simple surgery, says implantation can be conducted Tse. With a conventional without putting any electrodes defibrillator, more complicated into the heart through blood surgery must be used to replace vessels, leaving the heart worn-out electrodes, which may untouched,” says Professor Tse cause heart injuries. Hung-fat, William MW Mong Tse says the S-ICD costs Professor in Cardiology and Chair Professor of department of HK$200,000, similar to a midrange conventional ICD, medicine at the faculty. which costs between “Hence, the risk of heart HK$140,000 and HK$300,000. perforation, and/or infection of However, the new device has the heart after the surgery will only a five-year battery life, drop to zero per cent.” compared to seven to 10 years Three incisions over the for the conventional device. patient’s left chest are made and In Hong Kong, about the device, called a 200 patients install subcutaneous defibrillators every implantable cardiac year. They defibrillator (S-ICD), provide is placed under the immediate help skin of the chest to patients at wall, over the ribs critical and sternum. moments to A wire runs of patients with implants had avoid sudden under the skin

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cardiac arrest because of an insufficient outflow of blood from the heart. First introduced to clinical practice in 1980, the implantable cardiac defibrillator has improved the survival rate of patients at high risk for sudden cardiac death. Randomised, multicentre studies have shown a relative risk reduction in total mortality of up to 54 per cent and an arrhythmic mortality reduction of 50 per cent to 70 per cent. However, the most frequent complications associated with the conventional device involve the transvenous leads. The SICD was initially developed for patients who were not candidates for these conventional ICDs, such as those with some congenital heart abnormalities or no venous access. “With the failure rate of transvenous leads variably reported as 28 to 40 per cent at eight years, a subcutaneous approach could substantially reduce risks associated with lead extraction and is particularly suited to young patients with a long life expectancy and higher lead failure rates due to active lifestyles,” wrote Christopher P. Rowley and Michael R. Gold in their paper published in June 2012 in the journal Circulation: Arrhythmia and Electrophysiology.

no complications from the device after six months, a study found

Defibrillators shock the heart back to normal rhythm to avert the possibility of sudden cardiac arrest.

Asthma sufferers may be prone to bone loss There may be a link between asthma and a decrease in bone mineral density, according to a study by South Korean researchers in the journal Annals of Allergy, Asthma & Immunology. Among more than 7,000 patients studied, 433 of whom had airway hyperresponsiveness or asthma. In people with these conditions, lumber spine and thigh bone density was significantly lower than those without the conditions. The prolonged use of corticosteroids, the most effective asthma medication, is known to be a risk factor of osteoporosis. However, the findings of this study have to be further investigated, says allergist Dr John Oppenheimer, associate editor of the journal. Reasons for bone loss could include corticosteroid use, low levels of vitamin D or even race.

Different Implantable Cardioverter-Defibrillators

Subcutaneous ICD

Conventional ICD

Implanted under the skin on the side of the chest below the armpit

Implanted either in the upper chest or abdomen

Connected to electrode that is implanted under the skin along the rib margin

Connected to wires with electrodes that are inserted through vein in upper chest

Less invasive: leaves heart untouched and therefore fewer complications

Invasive: connected to heart chambers via transvenous leads, which cause the most frequent complications

Shocks the heart externally: cannot be used by patients who also need pacing

Shocks the heart internally: can perform long-term cardiac pacing

Sources: Boston Scientific, Journal of the American College of Cardiology

Due to the advantages of the subcutaneous approach, for some patients, it may be a preferred approach for the prevention of sudden cardiac death than simply an alternative to transvenous ICDs, added Rowley and Gold. Tse notes that the new device is not for everyone: “The S-ICD can replace the most important function of conventional ICD, that is, defibrillation, but cannot perform long-term cardiac pacing to maintain heart rate.” Patients who will benefit most from the new device include those with structural heart diseases in whom the leads cannot be implanted; those with high risk of infection, such as those on hemodialysis or immunosuppression; those with high risk of lead complication; and those who require primary prevention of sudden cardiac death and do not require pacing,

especially those with inherited cardiac arrhythmic syndrome or cardiomyopathy. The S-ICD is made by US company Boston Scientific and has been used in Europe and New Zealand since 2009. It was approved by the US Food and Drug Administration in 2012, following an extensive review of data obtained from pilot studies and the European EFFORTLESS S-ICD Registry.

SCMP

PROFESSOR TSE HUNG-FAT

In a study funded by the device’s maker and published last August in the American Heart Association journal Circulation, 314 patients using the device were followed for an average of 11 months. Three quarters of the participants were male, with an average age of 52. Over the first 180 days following implantation, 21 patients had 38 episodes of abnormal rhythms that precede cardiac arrest – ventricular fibrillation or ventricular tachycardia. In each case, the device restored the heart to a normal rhythm. During this time, 99 per cent of the patients had no complications from the device. But 41 patients (13 per cent) received an inappropriate shock. The ongoing European EFFORTLESS registry has confirmed these positive results. jeanette.wang@scmp.com

along with blood and the lining of the endometrium that has thickened in preparation of pregnancy. This process is called menstruation. With anovulation, there is no ovulation because progesterone is not produced. However, the oestrogen-induced endometrial accumulation continues, resulting in bleeding, which is mistaken for a period. Anovulation might be due to a number of factors, among them: stress and anxiety, certain types of medication, excessive exercise, extreme weight loss, obesity and hormonal imbalances (for example, when the pituitary gland or hypothalamus does not produce the hormones needed to trigger ovulation).

Anovulation accounts for about 10 per cent to 20 per cent of infertility cases, Ng says. If you have regular periods but are anovulatory, you will not experience the mid-cycle abdominal discomfort due to ovulation or the abdominal and breast tenderness due to the increase in progesterone levels after ovulation. If you are having trouble falling pregnant and suspect you may be anovulatory, it is important to get checked. Your doctor will order a blood test to measure your progesterone level about one week before your next expected period to confirm whether you have ovulated. A recent survey by the Family Planning Association found that Hong Kong couples have

The risk of heart perforation after surgery will drop to zero per cent

Extremes of sleep duration may affect memory Too much or too little sleep may result in worse memory in older age, finds a new study led by Brigham and Women’s Hospital in Boston. Women who slept five or fewer hours, or nine or more hours per day, either in midlife or later life, had worse memory, equivalent to nearly two additional years of age, than those sleeping seven hours per day. Women whose sleep duration changed by greater than two hours per day from middle age to older age also had worse memory than women with no change in sleep duration. The study, published in The Journal of the American Geriatrics Society, involved more than 15,000 female nurses aged 70 or above.

A fattening gene A team of researchers from Germany and Japan have discovered a gene that controls fat metabolism, possibly paving the way for the development of a drug that would prevent people becoming overweight. The researchers identified SIRT7, a gene from the sirtuin protein group that plays a major role in the utilisation of energy in a high-fat diet. They fed a high-fat diet to genetically modified mice that lacked the gene and also a control group. The mice without SIRT7 maintained their normal weight, while the controls put on significantly more weight.

HITS & MYTHS ................................................ Sasha Gonzales life@scmp.com Does having regular periods mean that ovulation is regular, too? The straight answer: No The facts: Some women take it for granted that just because they menstruate monthly it means that they are ovulatory and, therefore, will not have any problems falling pregnant. But the fact is, just because you have regular periods does not mean that you are ovulatory. Anovulation – which describes the condition when ovulation does not occur – is not common, but it is a problem for women who want to conceive.

According to Professor Ernest Ng Hung-yu, clinical professor of the department of obstetrics and gynaecology at the University of Hong Kong’s Li Ka Shing Faculty of Medicine, anovulation generally presents with irregular periods. If you have regular periods, you have a 95 per cent chance of ovulation. Therefore, you can be anovulatory even if your menstrual cycle is seemingly normal. Ovulation occurs when a mature egg is released from the ovary, a process triggered by the hormone progesterone. The egg then travels down the fallopian tube where it waits to be fertilised. If it is fertilised, conception occurs. Otherwise, the unfertilised egg is shed,

The process of ovulation inside a female body. Photo: Corbis

become more positive about childbearing, with the proportion of women wanting children rising significantly, from 12.7 per cent in 2007 to 20.2 per cent in 2012 – the highest since 1992. Correspondingly, the proportion that did not desire any or more children decreased, from 80.8 per cent in 2007, to 63.8 per cent in 2012. Despite these changing attitudes, birth and fertility rates in Hong Kong are still among the lowest in Asia, mainly because couples are getting married later or putting off having children. Another explanation for this trend is the misconception women have about their fertility, such as having a period means that ovulation has taken place.


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