Ivabradine

Ivabradine, Nicorandil, Ranolazine, Trimetazidine are new generation of antianginal drugs .The mechanism of action, principal adverse effects and contraindications of each drug will be discussed.

Ivabradine:
Mechanism Of Action:
Ivabradine blocks the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel which is responsible for the cardiac pacemaker I(f) current. In clinical electrophysiology studies, the cardiac effects were most pronounced in the sinoatrial (SA) node, but prolongation of the AH interval has occurred on the surface ECG, as has PR interval prolongation
Principal Adverse Effects:
-Bradycardia
-First- degree heart block , very rarely second and third degree heart block
- Ventricular extra systoles and very rarely
atrial fibrillation
-Headache
-Dizziness
-Visual disturbance including phosphenes and blurred vision
Contraindications:
-In heart failure if heart rate below 75 beats per minute or in decompensated acute heart failure
-Blood pressure < 30ml/min).
This is a summary of the principal recommendation for clinical practice arising from the journal "Should coronary Calcium Screening Be Used in Cardiovascular Preventive Strategies?" by Robert O. Bonow in the New England Journal of Medicine.
In the journal, Bonow begins by highlighting the Framingham risk score ,which was recommended by the Adult Treatment Panel III of the National Cholesterol Education Program , for assessing of individual risk factors and global risk . This score is categorized to ; low risk if less than 10 % , moderate risk for those having two or more risk factors and a 10 year risk of less than 10%, moderately high ( previously known as intermediate ) for those with a 10 to 20 % likelihood of having a coronary event during the next 10 years,and high risk if they have a coronary event or more than 20 % estimated likelihood of a coronary event over the next 10 years .
Studies evaluating the beniefets of using Coronary Calcium Screenig or the CAC score had mixed results . Two observational studies reported that the knowledge of positive CAC score was associated with a greater usage of statins and asprin therapy and reducing changes in lifestyle ,but these studies can prove cause and effect. However, another randomized trial ,revealed that individuals who were informed with the positive test results of CAC testing did not show any favorable improvement in their risk factor profile after 1 year compared to the individuals who were not informed.
Various guidelines were dicussed including the U.S.
Preventive Services Task Force which had a negative opnion about recommending CAC screening of low risk for coronary events individuals , due to the lack of evidence notwithstanding the fact that discion is still not made concerning a routine screening of those with high risk for events . The expert-panel statement from Preventive Conference V, sponsored by the American Heart Association in 2000 had a smiliar opnion for not recommending the routine CAC assement but it noted that CAC screening would have the greatest potential value among asymptomatic patients with intermediate Framingham risk score.
ATP III GUIDELINES also does not recommend the CAC screening , however it pointed out that CAC scoring might be reasonable to consider for advanced risk assessment in appropriately selected individuals with multiple risk factors provided by a physician who has sufficient knowledge about non invasive testing.
In conclusion, wether a widespread coronary calcium screening will lead to an overall improvement in quality of care and clinical outcome or it would cause unnessecary further testing , radation exposure and anixity for the patients ,this will remain a major argument .Therefore this issue needs to be addressed in the future trials focusing more on the clinical outcomes and cost
effectiveness.