represent contraindications. crt treatment should be considered in lieu of cardiac contractility modulation in patients with left bundle branch block (lbbb) and a qrs duration of over 120 ms, or when the qrs duration is greater than 150 ms and independent of lbbb. as with conventional pacemaker therapy, the cardiac contractility modulation device cannot be implanted if the leads cannot be positioned appropriately in the heart. in cases where there is an artificial heart valve between the right atrium and ventricle (a mechanical prosthetic tricuspid valve), the valve function could be greatly affected by the ventricular leads. in some instances it may be impossible to guide the leads through the main veins in the upper half of the body to the heart due to venous thrombosis, for example vvi pacemakers, in the case of 100% stimulation, are also contraindicated. side effects the most frequently encountered adverse events related to cardiac contractility modulation therapy are lead fracture or lead dislodgement. other reported complications include: infection and bleeding at the ipg implantation site accumulation of fluid in the pericardium (pericardial effusion) these side effects are similar to those that occur with other electrical stimulation therapies, such as pacemakers, crt devices or icd devices. furthermore, recorded complications did not differ between patients with activated or deactivated cardiac contractility modulation devices. overall, cardiac contractility modulation treatment was demonstrated to have no negative impact on health markers. precautions metal detectors used for security screening similarly to patients with other electrical stimulation devices, patients with a cardiac contractility modulation device must follow certain precautions arising from the device implantation and its function. electromagnetic fields: strong electromagnetic fields can interfere with the function of the device. most interference will lead to inhibition of cardiac contractility modulation signal delivery. once away from the field, the device will resume its normal function in most cases. the electromagnetic fields of household appliances are usually considered harmless. mobile phones: similarly to other electrical stimulation devices, such as pacemakers, aside from a recommended safety distance of 10–15 cm (4-6 inches) between the device and mobile phones, there are no restrictions on the use of mobile phones. security checks: full body or hand-held metal detectors, such as those used at airport security controls, do not usually affect the function of the device. however, where such detectors are used there are often signs warning people with cardiac pacemakers and defibrillators, and cardiac contractility modulation patients are therefore advised to present their device id. in these cases, the security check will typically continue with the use of a hand-held metal detector or by physical inspection. sports: all sports associated with increased stress on the arms or the chest, such as body building, martial arts or tennis, are usually not permitted. diving is only permitted up to a depth of 5 meters due to the high pressure at greater depth. magnetic resonance imaging (mri): similarly to other electrical stimulation devices, such as pacemakers, cardiac contractility modulation therapy is a contraindication for mri, a medical imaging technique. mechanism of action the mechanism of action of cardiac contractility modulation has been subject to continuous research since its initial discovery. based on animal testing and experiments on human myocardial tissue obtained by biopsies, essential parts of the mechanism of action have been identified. according to current understanding (as of february 2015), the mechanism of action of cardiac contractility modulation may be summarized in the following manner: the signals applied during the electrical non-excitatory state of the cardiac muscle cells (the absolute refractory period) cause an increase in myocyte calcium in the cytosol during systole. this increases the muscle contraction strength. additionally, within minutes, cell metabolism and gene expression, which are typically abnormal in heart failure, improve towards their normal state. this beneficial effect occurs initially only in the area adjacent to the electrodes, but with time also spreads to remote areas of the cardiac muscle. cardiac contractility modulation therefore restores the structure and function of damaged cells back towards their normal state. in some cases, disease-related changes in the ventricular heart structure can be partially reversed by cardiac contractility modulation through a process known as reverse remodeling of the heart. history development of cardiac contractility modulation began in the late 1990s. studies on individual cardiac muscle cells using a patch-clamp technique had already shown, in 1969, that a voltage applied during the absolute refractory period through leads between the interior of the cell and its outside environment increased the calcium influx through the cell membrane and improved the contraction of cardiac muscle cells. in 2001, scientists observed that a similar effect occurs even if the voltage is applied exclusively outside the cardiac muscle cells. additionally, it was observed that therapeutically useful effects on the cardiac muscle were achieved if the electrical signals were applied not only to single cells but to large areas using larger leads, as used in conventional cardiac pacemakers. the contractility of both a healthy heart and a damaged heart could be increased through application of appropriate signals during the absolute refractory period of the cardiac muscle cells. an implantable cardiac contractility modulation device was received by a patient for the first time in 2001. the first study on the therapeutic effects of in humans was presented in 2004. to date, more than 3,000 heart failure patients have been treated with cardiac contractility modulation worldwide, including 641 patients under the study conditions recommended by the cochrane collaboration as being necessary for inclusion in a meta-analysis. cardiac contractility modulation device implantation was first successfully done in india in royal hospital, trivandrum, kerala, under the leadership of dr. c. bharath chandran. advocate harishankar was the first person in india to get the cardiac contractility modulation device implanted.