Implantable cardioverter defibrillators (ICD) are life saving devices used for treatment of life threatening ventricular arrhythmias and averting sudden cardiac death.
Some of the rare adverse events which can occur with ICDs are as follows:
Generator pocket hematoma
Lead problems like insulation failure and fracture requiring lead revision
Infection, device pocket erosion
Inappropriate defibrillator discharge (inappropriate shocks), which could be due to T-wave oversensing, lead problems or supraventricular arrhythmias
Some may develop psychological problems due to undue fear for shocks
Functional mitral regurgitation (FMR) occurs due to non-coaptation of mitral leaflets in the setting of left ventricular dilatation. It can occur in cardiomyopathies of both ischemic and idiopathic varieties as well as in left ventricular dilatation due to aortic regurgitation. The distorted shape of the left ventricles restricts the mitral valve closure. Left ventricular remodeling is largely responsible for functional mitral regurgitation. There is increased sphericity of the left ventricle with longer tethering distance and enlarged mitral annulus. But the incidence of functional mitral regurgitation is less than what is expected from left ventricular remodeling. This is thought to be due to the enlargement of mitral leaflets in response to changes in left ventricular enlargement and change in morphology. Enlargement of mitral leaflets may not be due to stretch alone, but also due to active growth of cells and matrix. The enlargement of mitral leaflets causing a less than expect rate of functional mitral regurgitation is more likely to occur in slowly progressive left ventricular dilatation as in chronic aortic regurgitation. For this reason, the chance of functional mitral regurgitation is less in chronic aortic regurgitation than in other cases with corresponding severity of left ventricular dilatation [Beaudoin J et al, J Am Coll Cardiol. 2013;61:1809-1809].
90.7% freedom from recurrent severe mitral regurgitation was documented at twenty years after mitral valve repair in a study by David TE et al [Late outcomes of mitral valve repair for mitral regurgitation due to degenerative disease. Circulation. 2013;127:1485-1492]. They had prospectively followed up eight hundred and forty patients who underwent mitral valve repair for mitral valve regurgitation due to degenerative disease fro 1985 to 2004. Age, functional class and left ventricular ejection fraction predicted late cardiac mortality and valve related mortality. In those in functional class IV at the time of surgery, mitral valve repair failed to normalize the life span. The probability of reoperation at twenty years was around six percent. Freedom from moderate or severe mitral regurgitation was around seventy percent. Predictors of recurrent mitral regurgitation were age, isolated prolapse of anterior mitral leaflet and the severity of myxomatous degeneration in the mitral valve. Longer duration of cardiopulmonary bypass time was also associated with higher risk of recurrent mitral regurgitation. The chance of recurrent mitral regurgitation was reduced by mitral annuloplasty.
Radiation associated heart disease is more noted in survivors of breast cancer and Hodgkin’s disease who had undergone radiotherapy with incidental radiation to the heart. The risk is higher in those who received chemotherapy with agents like anthracyclines in addition to radiation. The features of radiation-associated heart disease could involve all the three layers of the heart with pericarditis, myocardial fibrosis or dysfunction, and valvular damage. Radiation is one of the few conditions, which can cause co-existence of restrictive heart disease with constrictive pericarditis. The conduction system of the heart can also be involved in radiation-associated heart disease. Higher doses and younger age at therapy as well as longer follow up will increase the cumulative incidence of radiation-associated heart disease. Advances in radiotherapy techniques can certainly reduce the dose and volume of exposure to the heart and help in lowering the risk of radiation-associated heart disease.
Mandawat A and colleagues [Safety of Pacemaker Implantation in Nonagenarians. An Analysis of the Healthcare Cost and Utilization Project-Nationwide Inpatient Sample. Circulation. 2013;127:1453-1465.] retrospectively analyzed the data of over one lakh patients aged more than seventy years who had undergone initial pacemaker implantation between 2004 and 2008. Eleven percent of them were nonagenarians (ninety or more years of age). Compared to septuagenarians (70 – 79 years) nonagenarians were more likely to have moderate or severe comorbidities and more likely to be admitted on an emergency basis. While unadjusted mortality and complication rates in septuagenarians were 0.6% and 5.61%, it was 1.87% and 6.31% in nonagenarians. But multivariable analysis revealed that severe comorbidity was a greater predictor of mortality than increasing age. There was also similar association between severe comorbidity and complications. The authors concluded that even though older age predicts poorer outcome, the absolute rates are modest even in nonagenarians and the stronger predictor of poor outcome was comorbidity rather than age.
J. Matthew Brennan and associates from Duke Clinical Research Institute [Long-Term Safety and Effectiveness of Mechanical versus Biologic Aortic Valve Prostheses in Older Patients: Results from the Society of Thoracic Surgeons (STS) Adult Cardiac Surgery National Database. CIRCULATION. Published online before print March 28, 2013,] studied the Society of Thoracic Surgeons Adult Cardiac Surgery Database for those between sixty five and eighty years who underwent aortic valve replacement at six hundred and five centres in the nineteen nineties. There were over twenty four thousand who had undergone biopresthetic implant while there a little less than fifteen thousand had a mechanical prosthesis. Both groups had similar age adjusted risk of death while the risk of reoperation and endocarditis was higher with the bioprosthetics. At the same time, the risk of stroke and bleeding were lower in those with bioprosthetic valves than mechanical valves.
A new combination catheter system with ability for intravascular ultra sound imaging (IVUS) along with near-infrared spectroscopic imaging (NIRS) has been developed as the TVC Imaging System TM (MC 7 system, InfraReDx, Burlington, Massachusetts). NIRS is able to detect lipid rich core of the plaques and assigns red colour to low probability and yellow colour to high probability. IBIS-3 (Integrated Biomarker and Imaging Study 3) [Simsek C et al. EuroIntervention. 2012 Jun 20;8(2):235-41. The ability of high dose rosuvastatin to improve plaque composition in non-intervened coronary arteries: rationale and design of the Integrated Biomarker and Imaging Study-3 (IBIS-3)] evaluating the effect of rosuvastatin on lipid rich coronary plaques is utilizing this combo catheter.
NIRS imaging is done with a motorised catheter pull back at a speed of 0.5 millimeter per second. The amount of lipid core plaque is displayed as a chemogram with pull back position in millimeters on x-axis and the circumferential position of the measurement in degrees on on the y-axis as if the coronary vessel is split open on the longitudinal axis. Red pixels indicates no lipid and yellow pixels indicates more than 60% while black indicates lack of enough data. NIRS derived lipid core burden index (LCBI) score is calculated by multiplying the fraction of valid yellow pixels by 1000.
Some of the newer imaging modalities for assessing coronary atherosclerosis beyond conventional coronary angiography (CAG), computerized tomographic coronary angiography (CTCA) and intravascular ultrasound (IVUS) are:
OCT: Optical coherence tomography
NIRS: Near-infrared spectroscopic imaging
Intravascular magnetic spectroscopy
Intravascular magnetic resonance imaging
IVPA: Intravascular photoacoustic imaging
NIRF: Near-infrared fluorescence imaging
TRFS: Time resolved fluorescence spectroscopic imaging
Of these, OCT is available for use in many centers across the globe while most of the other modalities are still available only as research tools. Each modality can have its own advantages. If IVUS can image beyond lipid rich plaques, OCT can penetrate calcified plaques.
A large randomized clinical trial involving over four thousand seven hundred patients from seventy nine centres across nineteen countries has been published in NEJM [Lamy A et al. Effects of Off-Pump and On-Pump Coronary-Artery Bypass Grafting at 1 Year. N Engl J Med 2013; 368:1179-1188]. One year after coronary artery bypass grafting, there was no significant difference between on pump and off pump bypass surgery in the rate of repeat revascularisation, quality of life or neurocognitive function. The same group had reported earlier that there was no significant difference in the composite outcome of myocardial infarction, death, stroke and new onset renal failure requiring dialysis support.
Detection of vegetations on prosthetic material within the heart is often difficult as these structures may cause acoustic shadowing and reverberation artifacts. Even though trans esophageal echocardiography (TEE) is better than trans thoracic echocardiography (TTE) in detecting intracardiac vegetations, intracardiac echo may have an additional advantage due to the higher resolutions possible. Intracardiac echo (ICE) uses transducer frequencies in the range of 5.5 – 10 MHz and the probe is usually a 10F device, which can be introduced into the right sided cardiac chamber through the femoral vein and inferior vena cava. A recent study by Maria Lucia Narducci et al [Usefulness of Intracardiac Echocardiography for the Diagnosis of Cardiovascular Implantable Electronic Device–Related Endocarditis. J Am Coll Cardiol. 2013;61(13):1398-1405.] evaluated over one hundred and sixty two patients who underwent lead extraction, of which one hundred and fifty two had device related infection and ten had lead malfunction. The detection of intracardiac masses suggesting vegetations were higher with ICE than with TEE.