A 'sensor' under the skin records silent arrhythmias and helps prevent many strokes

Researchers of the Catholic University – Policlinico A. Gemelli of Rome together with colleagues of the Campus Bio-Medico University Hospital of Rome and 55 centers in Europe, Canada and the USA have devised a way to prevent many cases of stroke or especially their recurrences: yes it is a 'sensor' which, placed under the skin, records arrhythmias 'invisible' to traditional and asymptomatic diagnostic methods, therefore more subtle because they are not recognised. Quite a few cases of stroke - apparently without a cause - can be linked to these so-called 'paroxysmal' arrhythmias, because they resolve spontaneously and are symptom-free. Thanks to the device, by recording this type of heartbeat defect in real time when it occurs, the doctor can promptly proceed with preventive anti-stroke therapy and avert the worst.
Published in the prestigious 'New England Journal of Medicine', the CRYSTAL AF study (CRYptogenic STroke And underLying atrial fibrillation) represents the largest global clinical trial on this front and was conducted by Professor Tommaso Sanna, Cardiologist at the Department of Cardiovascular Sciences of the Policlinico A. Gemelli directed by Professor Filippo Create, in collaboration with Professor Vincenzo Di Lazzaro, head of the Complex Operative Unit of Neurology at the Campus Bio-Medico University Hospital of Rome.

The protagonist of this multicenter research success is a diagnostic system already in use worldwide for other types of patients: it is a microdevice, smaller than a USB 'pen', for the continuous recording of cardiac activity, implanted subcutaneously under local anesthesia. The tiny monitoring system can be 'interrogated' directly by the patient, through a remote control equipped with a red light. The turning on of the light indicates that a cardiac arrhythmia is in progress. Thus, the subject can promptly go to a hospital for further tests. The device is also capable of transmitting the patient's electrocardiogram by telephone to the specialist. The latter, if the diagnosis of arrhythmia is confirmed, has the elements in hand to intervene with adequate preventive therapy.
In Italy a stroke occurs every three minutes. This disease represents the third cause of death and the most frequent cause of permanent disability in adults, because only 25% of the surviving patients recover completely and over 50% are affected by a deficit that makes them no longer self-sufficient. The main causes of the onset of stroke are arterial hypertension, heart disease, diabetes mellitus, hypercholesterolemia, cigarette smoking and stenosis of the carotids, i.e. the most important arteries that carry blood to the brain.

To complicate matters there is the fact that stroke often occurs without alarm bells, catching doctor and patient alike and making timely treatment more difficult. In these cases we speak of 'cryptogenic' or stroke with no apparent cause. They experience it between 40 and 80 thousand Italians every year, i.e. between 20 and 40% of the almost 200 people affected annually by this serious pathology in our country (processing on Ministry of Health data). In reality, behind these cryptic strokes there is a cause, often subtle because without symptoms: atrial fibrillation. In fact, studies have shown that atrial fibrillation increases the risk of having an ischemic stroke by 4 to 5 times and this applies both to paroxysmal atrial fibrillation (that is, which resolves spontaneously), persistent (which is interrupted following a treatment of cardioversion), or permanent (which can no longer be stopped). Unfortunately, precisely because atrial fibrillation is very often paroxysmal (that is, it lasts for a variable period of time and stops spontaneously) and asymptomatic, it becomes difficult to identify with traditional diagnostic techniques such as the electrocardiogram or the 24-hour Holter which records heart activity for 24 hours).

"With our studio – explains Prof. Sanna, first author of the work – we observed that within 3 years of an ischemic stroke with no known cause, 30% of patients have at least one episode of atrial fibrillation, almost 80% of which are asymptomatic”. This means that precisely that type of atrial fibrillation could be the basis of the first stroke, but also that the patient is at risk of having a second one.

"In the three years of observation of the Approximately 500 stroke patients with no defined cause enrolled for the study – explains Prof. Sanna – was 30% of implanted patients experienced atrial fibrillation versus 3% of non-implanted patients. A fact that demonstrates the clear superiority of this diagnostic strategy compared to the traditional approach”. In fact, the device records atrial fibrillation in a number of patients 7,3 times greater than traditional methods at 12 months of observation and 8,8 times greater at 36 months.

"Moreover – reiterates the expert – atrial fibrillation was asymptomatic in 80 percent of patients and, therefore, without the microdevice it would have escaped diagnosis. Not only that, the occurrence of the arrhythmia proved to be somewhat unpredictable, as in some patients it was recorded a few weeks after the stroke, while in others even a year after the event".

"The results of the study – adds the Prof. Di Lazzaro - open a new, very interesting front in the field of secondary prevention of cerebral stroke. About a quarter of strokes, in fact, recur as a recurrence, with far more devastating consequences than the first event. To prevent its recurrence, it is essential to try to define its cause. The most commonly used drugs, such as aspirin, belong to the category of antiplatelet agents and have limited effectiveness in preventing stroke caused by atrial fibrillation. Thanks to the information provided by this microdevice, the specialist, having evaluated all the risk factors, will be able to promptly prescribe a therapy with anticoagulants, much more effective in preventing embolism". 

Where the cause of the stroke is not identified, therefore, it may be considered in the near future installation of this device. It will obviously be important to carry out a careful selection of patients, using a screening initial with all diagnostic investigations already consolidated for the search for the causes of the stroke, in order to limit costs for the National Health System. Note, on the other hand, that this approach could reduce the costs related to stroke recurrences, which can be avoided thanks to the identification of patients at risk.