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CARDIOLOGY - Publications
Vol. 2 Issue 13
Page updated on 24th November 2004 |
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ACP/AAFP Guidelines for Management of Atrial Fibrillation |
A joint commission of the American College of Physicians (ACP) and the American Academy of Family Physicians (AAFP) has issued six recommendations for internists and family physicians to manage patients with atrial fibrillation (AF) in a clinical practice guideline published in the December 16, 2003 issue of the Annals of Internal Medicine .
“The generally accepted practice has been to do everything we can to get patients back into sinus rhythm and to try to keep them there,” panel co-chair Michael LeFevre, MD, said in a news release. “The best available research showed that the preferred approach for most patients with AF should be to focus on control of heart rate and stroke prevention with blood thinners, rather than attempt to restore sinus rhythm. Controlling rhythm was not better than controlling rate in reducing complications and death, and the side effects of medication to keep patients in normal rhythm may be greater than the benefits.”
The Recommendations are as follows: |
Recommendation 1: Rate control with chronic anticoagulation is the recommended strategy for the majority of patients with AF. Rhythm control has not been shown to be superior to rate control (with chronic anticoagulation) in reducing morbidity and mortality and may be inferior in some patient subgroups to rate control. Rhythm control is appropriate when based on other special considerations, such as patient symptoms, exercise tolerance and patient preference.
Recommendation 2: Patients with
AF should receive chronic anticoagulation with adjusted-dose warfarin, unless they are at low risk of stroke or have a specific contraindication to the use of warfarin (thrombocytopenia, recent trauma or surgery, alcoholism).
Recommendation 3: For patients with AF, following drugs are recommended for their demonstrated efficacy in rate control during exercise and while at rest: atenolol, metoprolol, diltiazem, and verapamil (drugs listed alphabetically by class). Digoxin is only effective for rate control at rest and therefore should only be used as a second-line agent for rate control in atrial fibrillation.
Recommendation 4: For those patients who elect to undergo acute cardioversion to achieve sinus rhythm in AF, both direct-current cardioversion and pharmacological conversion are appropriate options.
Recommendation 5: Both transeso-phageal echocardiography with short-term prior anticoagulation followed by early acute cardioversion (in the absence of intracardiac thrombus) with postcardioversion anticoagulation versus delayed cardioversion with pre- and postanticoagulation are appropriate management strategies for those patients who elect to undergo cardioversion.
Recommendation 6: Most patients converted to sinus rhythm from AF should not be placed on rhythm maintenance therapy since the risks outweigh the benefits. In patients whose quality of life is compromised by AF, the recommended pharmacologic agents for rhythm maintenance are amiodarone, disopyramide, propafenone, and sotalol (drugs listed in alphabetical order). The choice of agent predominantly depends on specific risk of side effects based on patient characteristics.
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These recommendations for internists and family physicians to manage patients with AF do not apply to patients with postoperative or post-myocardial infarction AF, class IV heart failure, or valvular disease, or to patients already taking antiarrhythmic drugs.
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Carvedilol Reverses Left Ventricular Remodeling in Chronic Heart Failure
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Treatment with carvedilol significantly improves left ventricular volumes and function in patients with chronic stable heart failure , as reported in the July 2004 issue of Heart .
“This is important,” senior investigator
Dr. Dudley J. Pennell, Royal Brompton Hospital , London , told, “because it is well established that the larger the heart, the worse the patient's prognosis.”
Dr. Pennell and his colleagues noted that the ability of beta-blockers to improve left ventricular ( LV ) function has been shown previously, “but data on the effects on cardiac remodeling are limited.”
The researchers investigated the effects of carvedilol on LV remodeling in 34 patients with chronic stable heart failure and LV systolic dysfunction caused by coronary artery disease in this CHRISTMAS (Carvedilol Hibernating Reversible Ischaemia Trial: MArker of Success) substudy. All underwent cardiovascular magnetic resonance before and 6 months after randomization to carvedilol or placebo. The main outcome measure was LV remodeling at 6 months.
Compared with placebo-treated patients, carvedilol-treated patients had significant reductions in LV end systolic volume index (LVESV 1 ) and LV end diastolic volume index (LVEDV 1 ). They also had a significant 3% increase in LV ejection fraction (LVEF) versus a drop of 2% in placebo patients (Figure 1).
By reducing the heart size,” Dr. Pennell pointed out, “the stress in the wall of the heart is reduced which allows the heart to function more effectively. In addition, because carvedilol is a beta blocker, it slows the heart rate and this allows more time for nutrient blood flow to reach the heart muscle.”
“The combination therefore, of reduced size and slowed heart rate,” he concluded, “is very helpful in improving symptoms and longevity in heart failure.” These effects might contribute to the benefits of carvedilol on mortality and morbidity in patients with chronic heart failure.
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New Noninvasive Test For Women With Chest Pain
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A new noninvasive test shows potential for helping women with unexplained chest pain, according to a study published in the June 22, 2004 issue of Circulation .
Women present more often than men for the evaluation of chest pain symptoms, and half of all women with chest pain undergoing coronary angiography do not have coronary artery disease (CAD), compared with 17% of men. “We have seen that many of these women are admitted to the hospital for chest pain, and undergo angiography to look for CAD behind the angina, yet no such disease is found,” said Gerald M. Pohost, M.D., University of Southern California and senior author of the study. “Our results indicate that in many of these women, something is keeping the heart from getting the oxygen it needs. We suspect microvascular dysfunction or disease.”
The study was a part of the Women's Ischemia Syndrome Evaluation (WISE), a four-center study of women undergoing coronary angiography for chest pain or suspected myocardial ischemia. The researchers compared 352 women with CAD to 74 other women without it. These CAD-free women underwent an imaging scan called phosphorus-31 nuclear magnetic resonance spectroscopy (MRS) whereby the women squeeze a handgrip while lying inside an MRI unit. Nuclear MRS technology enables to measure levels of two phosphates found in heart tissue, once at rest and again while squeezing the handgrip (experiencing physical stress).
Researchers found that the ratio of the two phosphates, phosphocreatine and ATP declined significantly in 14 of the 74 CAD-free women when they squeezed the handgrip. “A big drop in the ratio is abnormal and a sign that heart tissue is not getting enough blood,” Pohost explained.
In order to find a link between abnormal results and women's cardiovascular health, investigators tracked women who experienced a cardiovascular event (myocardial infarction, stroke, other vascular events or hospitalization for unstable angina) over the next three years. Results showed that women with no CAD/normal MRS had the highest cumulative 3-year freedom from event (87%). Women with no CAD/abnormal MRS and women with CAD had significantly poorer freedom-from-events rates (57%, p=0.009 and 52%, p<0.0001, respectively). Freedom-from-events rates were similar for women with no CAD/abnormal MRS and women with CAD (57% versus 52%, p=0.42).
The study concluded that among women without CAD, abnormal MRS consistent with myocardial ischemia predicted cardiovascular outcome, notably higher rates of anginal hospitalization, repeat catheterization, and greater treatment costs. Magnetic resonance spectroscopy could be used to evaluate women complaining of chest pain, and even may reduce the number of women undergoing repeated coronary angiography procedures.
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ACE Inhibitors Reduce the Occurrence of Atrial Fibrillation in Hypertensives
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Angiotensin converting enzyme (ACE) inhibition was associated with a reduced incidence of atrial fibrillation (AF) in hypertensive patients, as published in July 7, 2004 issue of Journal of the American College of Cardiology .
Recent reports have identified a clear association between hypertension and AF. Indeed, hypertension is present in a majority of patients diagnosed with AF and is responsible for more cases of AF (14%) than any other risk factor.
In this retrospective, longitudinal, cohort study, researchers Dr. Tardif JC, Montreal Heart Institute, Quebec, Canada and his coworkers evaluated the effects of ACE inhibition versus long-acting calcium channel blockers (CCB) on the occurrence of AF in 10,926 hypertension patients (mean age 65 years).
The study showed that the incidence rate of new-onset AF during the entire study follow-up period of 4.5 years was less in the ACE inhibitor group as compared with the CCB group (17.9 vs. 18.9 per 1,000 patient-years) with a hazard ratio of 0.85 (95% confidence interval [CI]: 0.74 to 0.97) in the ACE inhibitor group. ACE inhibitors significantly increased the time to new-onset AF (29.5 months) as compared to CCB (26.1 months). The absolute incidence of AF was 10.6% versus 13.0% at six years and 19.4% versus 22.1% at seven years in the ACE inhibitor and CCB groups, respectively. The incidence rate of AF-related hospitalizations significantly reduced in the ACE inhibitor group as compared with the CCB group (8.5 vs. 11.9 per 1,000 patient-years) (Figure 1). Also, there was an incremental benefit of ACE inhibitor to prevent AF related hospitalizations in patients with a prior diagnosis of this arrhythmia as compared with those without.
Angiotensin II is a potent promoter of fibrosis, leading to cardiac myoblast proliferation and reduced collagenase activity. Atrial fibrosis is a frequent finding in patients with AF, which may explain intraatrial conduction disturbances and the persistent susceptibility for AF. Angiotensin II has also been shown to modify electrophysiologic remodeling. Inhibition of endogenous angiotensin II has been shown to prevent atrial effective refractory period shortening and loss of atrial effective refractory period rate adaptation during rapid atrial pacing. These results taken together provide two plausible explanations for the preventive effects of ACE inhibitors against AF, namely via prevention of structural and electrophysiologic remodeling.
“Although a beneficial effect of ACE inhibitor on AF has been convincingly demonstrated in patients with LV systolic dysfunction, hypertension is a much more prevalent condition, and extending the clinical benefits of ACE inhibitors to this patient population has important clinical implications. Our results suggest that treatment of hypertension with ACE inhibitors rather than other antihypertensive medications may significantly decrease the occurrence of AF,” concluded the researchers.
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Trimetazidine Improves Myocardial Function in Diabetics With Heart Failure
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Trimetazidine Improves Myocardial Function in Diabetics With Heart Failure Trimetazidine treatment in patients with diabetes and chronic heart failure can slightly improve systolic myocardial function at rest and during exercise, as published in July 2004 issue of Journal of Cardiovascular Pharmacology . In this pilot study, Inga S. Thrainsdottir, MD, Department of Cardiology, Karolinska Hospital, Stockholm, Sweden, and colleagues, assessed diastolic and systolic myocardial function in patients with type 2 diabetes and heart failure who were receiving trimetazidine along with the conventional treatment.
Twenty patients with diabetes mellitus (DM) and stable chronic heart failure (CHF) [New York Heart Association (NYHA) class II-III] due to ischemic heart disease participated in this randomised, double-blind crossover study. Mean age for the group of 20 patients was 66 years, average diabetes duration was 10 years and mean haemoglobin A 1c (HbA 1c ) was 6.6%.
After receiving a placebo for a 2-week run-in period, patients were randomised to trimetazidine (20 mg 3 times a day) or to a matching placebo for 4 weeks, followed by a 2-week washout period. The patients were then switched to the opposite treatment for another 4 weeks.
Exercise tolerance test, echocardiography, and tissue Doppler imaging (TDI) at rest and exercise were performed before and during treatment. Blood samples were obtained before and at the end of each treatment period. Echocardiography, TDI, exercise tests, and laboratory findings were used to analyse 19 patients after the first treatment period and 14 patients after both treatment periods of the crossover study.
In the 19 patients who completed the first treatment period, those initially randomised to trimetazidine had a significantly higher maximum work tolerance and time to onset of dyspnoea at baseline compared with those who received placebo first. Data from the echocardiograms of the 14 patients who completed both treatment periods revealed that ejection fraction at rest and after moderate exercise improved significantly during trimetazidine treatment compared with placebo. TDI velocities did not change significantly between treatment groups.
“This pilot study demonstrates that trimetazidine to some extent improved left ventricular ejection fraction in patients with type 2 diabetes and heart failure both at rest and exercise compared with the outcome of placebo,” the authors concluded.
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New Cardiac Arrhythmia Syndrome Identified
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An international team led by researchers from Duke University Medical Center and the Howard Hughes Medical Institute (HHMI) have defined a previously undescribed inherited cardiac arrhythmia syndrome that can lead to sudden death and can strike young, seemingly healthy people. The study results have been published in the May 31, 2004 issue of Proceedings of the National Academy of Sciences .
This arrhythmia has been ascribed to a mutation in a specific gene called ankyrin-B, which encodes a protein within heart muscle cells. Normally, ankyrin-B acts as a biochemical choreographer, ensuring that ion channels are correctly positioned in heart muscle cells, thereby regulating the electrical activity of the heart. When the gene is mutated, the channels are dislocated, leading to abnormal heartbeats.
“When taken together with the results of our earlier studies, the current findings support a new paradigm for human disease based on the abnormal coordination of these related ion channels,” said Vann Bennett , MD , senior member of the research team. “We now have a new class of arrhythmias that had in the past been grouped with the Long QT Syndrome (LQTS) class of arrhythmias. We can now say that the new syndrome is completely separate and distinct.”
The researchers believe that ankyrin-B mutations are more common than previously suspected, so they advocate that all family members of patients with sudden cardiac death undergo genetic testing. However, unlike other disorders with demonstrated genetic links but with no current treatments, the researchers said that beta blockers should be quite effective in controlling the irregular heartbeats.
“In the past, researchers have been investigating mutations in the channels themselves, and not how they are coordinated and work together as a unit. If we can better understand the cellular mechanisms behind their actions, we should be able to develop promising new therapies for a variety of diseases,” reported the authors.
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