The ABCs of managing systolic heart failure: Past, present, and future

Beta-blockers

In heart failure, there is increased sympathetic activation and associated elevations in norepinephrine levels, which may lead to deleterious long-term effects on cardiac function and structure. Beta-adrenergic receptor blockade is now known to be cardioprotective, but it was not always so; beta-blockers used to be contraindicated in patients with heart failure.

An early experience using beta-blockers in heart failure was described in 1975.^18,19 The first study to report a survival benefit of treating systolic heart failure with a beta-blocker was published in 1979.²⁰ Later, small controlled trials demonstrated a reduction in heart failure symptoms and improvement in left ventricular function and in NYHA functional class.²¹ Larger clinical trials have demonstrated a tremendous survival benefit with beta-blockers in heart failure, specifically carvedilol, extended-release metoprolol, and bisoprolol.

The US Carvedilol Heart Failure Study Group trial²² evaluated whether beta-blocker use in heart failure patients would reduce the rates of morbidity and mortality.²² The trial included 1,094 patients with symptomatic heart failure for at least 3 months and a left ventricular ejection fraction of 35% or less on background therapy including vasodilators, ACE inhibitors, and digoxin. Patients were randomized to receive either carvedilol or placebo. Carvedilol use was associated with a dramatic 65% risk reduction in mortality (7.8% with placebo vs 3.2% with carvedilol, P < .001) and a 27% risk reduction in hospitalizations (19.6% vs 14.1%, P = .036), leading to early trial termination.

CIBIS-II (the Cardiac Insufficiency Bisoprolol Study II)²³ investigated the effects of beta-blockers on survival and morbidity. CIBIS-II included 2,647 NYHA class III or IV patients with a left ventricular ejection fraction less than 35% on background medical therapy that included diuretics and ACE inhibitors. This trial was also terminated early, after demonstrating a significant survival benefit with bisoprolol.

MERIT-HF (the Metoprolol Extended Release Randomized Intervention Trial in Congestive Heart Failure)²⁴ evaluated if once-daily metoprolol would lower mortality rates  in patients with symptomatic heart failure. The study enrolled 3,991 NYHA class II–IV patients with chronic heart failure and a left ventricular ejection fraction of 40% or less. Like the previous two beta-blocker trials, MERIT-HF was terminated early, as it demonstrated a 34% reduction in all-cause mortality (7.2% risk of death per patient-year vs 11.0%, P = .00009).

The beta-blocker trials have shown that when added to background therapy, beta-blockers improve survival and reduce hospitalizations. However, when prescribing a beta-blocker, it is important to understand that not all beta-blockers are equal in the treatment of heart failure.

COMET (the Carvedilol or Metoprolol European Trial)²⁵ was the only head-to-head randomized control trial evaluating clinical outcomes in patients receiving carvedilol or metoprolol tartrate (not metoprolol succinate). In COMET, 1,511 patients with NYHA class II, III, or IV heart failure with a left ventricular ejection fraction of 35% or less were randomized to carvedilol or metoprolol tartrate. The primary end point of all-cause mortality occurred in 34% of the carvedilol group and 40% of the metoprolol tartrate group (P = .0017). There was no significant difference with regard to the composite end point of mortality and all-cause admissions.

Recommendations. The 2013 guidelines give a class IA recommendation for starting a beta-blocker (carvedilol, bisoprolol, or metoprolol succinate, Table 6) in patients with current or prior symptoms of heart failure.¹ Beta-blockers should be initiated with caution or avoided in patients with acutely decompensated heart failure with evidence of fluid overload.

Brain-type natriuretic peptide

Brain-type natriuretic peptide (BNP) or its amino-terminal cleavage product (NT-proBNP) originates in cardiomyocytes and is released by several triggers, most commonly cardiomyocyte stretch in the setting of volume or pressure overload.²⁶ The biologic significance of BNP includes natriuresis and vasodilation, renin-angiotensin system inhibition, and sympathetic nervous system modulation.²⁶

TIME-CHF (the Trial of Intensified vs. Standard Medical Therapy in Elderly Patients With Congestive HF)²⁷ investigated whether 18-month outcomes would be better if treatment were guided by N-terminal BNP levels rather than by symptoms. The BNP-guided strategy was not associated with a reduction in hospitalization or a survival benefit.

BATTLESCARRED (the NT-proBNP-Assisted Treatment to Lessen Serial Cardiac Readmissions and Death trial)²⁸ in 2009 showed that a BNP-guided management strategy significantly reduced mortality rates in patients under age 75 compared with standard medical therapy.

PROTECT (the Use of NT-proBNP Testing to Guide HF Therapy in the Outpatient Setting study)²⁹ also showed that a BNP-guided strategy was superior to usual care and was associated with reduced cardiovascular events and improved quality of life.²⁹

GUIDE IT-HF (the Guiding Evidence Based Therapy Using Biomarker Intensified Treatment in Heart Failure study), currently ongoing, is designed to assess the safety, efficacy and cost-effectiveness of a biomarker-guided strategy in 1,100 high-risk patients with heart failure with reduced ejection fraction. 

Recommendations. The 2013 ACC/AHA guidelines give a class IA recommendation for the use of BNP to support clinical decision-making, particularly in cases of clinical uncertainty.¹ BNP can also be used to establish prognosis or disease severity in chronic heart failure and to achieve optimal dosage of goal-directed medical therapy for euvolemic patients followed in a structured heart failure program.¹

Heart failure clinics

Continuity of care upon discharge from the hospital is currently in a state of evolution. Those diagnosed with heart failure can now experience more comprehensive posthospital care by virtue of disease management clinics. The name may vary by institution, but whether it is called a “diuresis clinic,” “bridge clinic,” or “heart failure clinic,” the goal is to improve guideline-driven care, educate the patient, and reduce heart failure hospitalizations. Heart failure clinics are designed to provide a smooth transition from inpatient to outpatient care and to encourage patient self-accountability in health maintenance thereafter.

Studies have shown that heart failure clinics are associated with better medication dosing, fewer hospitalizations, and lower healthcare costs.^30–32

Chronotropy: I_f inhibition

An elevated resting heart rate has been shown to be associated with increased cardiovascular morbidity and mortality.³³ Studies have shown that slowing the heart rate improves myocardial contraction and energy supply and reduces energy expenditure.³⁴ Ivabradine, a selective I_f (the f is for “funny”) channel inhibitor, slows the heart rate without other known cardiovascular effects.

SHIFT (the Systolic Heart Failure Treatment With the I_f Inhibitor Ivabradine Trial)³⁵ investigated whether isolated heart rate reduction with ivabradine would reduce adverse clinical outcomes in patients with symptomatic heart failure. SHIFT randomized 6,505 patients with a left ventricular ejection fraction of 35% or less, in sinus rhythm, with a heart rate of at least 70 beats per minute, on optimal medical therapy, and hospitalized within 12 months of enrollment to receive ivabradine or placebo. The primary end point was a composite of cardiovascular mortality and hospital admission for worsening heart failure. Outcomes varied by heart rates achieved, with the best outcomes in those with the lowest heart rates at trial conclusion.

Ivabradine (Table 7) is indicated for patients with symptomatic heart failure with a left ventricular ejection fraction less than 35%, in sinus rhythm, with a resting heart rate of at least 70 beats per minute, and either on a maximally tolerated beta-blocker or with a contraindication to beta-blockers.

Ivabradine should be avoided in patients who are in acute decompensated heart failure or are hypotensive (blood pressure < 90/50 mm Hg), as well as in patients with a significant conduction abnormality (sick sinus syndrome, sinoatrial block, third-degree atrioventricular block), hepatic impairment, or bradycardia (resting heart rate < 60 beats per minute).

Digoxin

Digoxin has been used in treating systolic heart failure for more than 70 years.^36,37

DIG (Digoxin Investigative Group trial)³⁸ evaluated the long-term effect of digoxin on rates of mortality and hospitalization for heart failure over a 3-year period. In patients with  a left ventricular ejection fraction less than 45%, digoxin had no effect on overall mortality when combined with diuretics and ACE inhibitors. However, the risk of hospitalization for worsening heart failure was significantly reduced with digoxin treatment.³⁸

Recommendations. Digoxin should be considered when patients are on guideline-recommended therapy but heart failure symptoms persist. It is commonly initiated at a dose of 0.125 to 0.25 mg. The target therapeutic range for digoxin is 0.5 to 0.9 ng/mL.¹ Digoxin toxicity can occur in patients with renal impairment, hypokalemia, hypomagnesemia, and hypothyroidism.

The 2013 ACC/AHA guidelines give a class IIA recommendation (treatment is “reasonable”) for digoxin in patients with heart failure with reduced ejection fraction unless contraindicated, to decrease hospitalizations for heart failure.¹

Diuretics

Clinical manifestations of volume overload in patients with heart failure are from excess salt and water retention leading to inappropriate volume expansion in both the vascular and extravascular space. Diuretics (Table 8) are the foundation of heart failure treatment. Most patients are first initiated on a combination of a loop diuretic and a low-sodium diet to improve symptoms.

The 2013 ACC/AHA guidelines give a class I recommendation for diuretics in patients with heart failure with reduced ejection fraction who have evidence of fluid retention, unless contraindicated, to improve symptoms.¹

Devices: ICDs

Patients with heart failure are at increased risk of sudden death and ventricular arrhythmias.³⁹ Previously, antiarrhythmic drugs were considered the standard of care for nonsustained ventricular tachycardia after myocardial infarction.

MADIT (the Multicenter Automatic Defibrillator Implantation Trial) investigated whether prophylactic implantation of an internal cardiac defibrillator would improve 5-year survival rates in patients with heart failure. Eligible patients had had a Q-wave or enzyme-positive myocardial infarction within 3 weeks of study entry. They also had had an episode of asymptomatic nonsustained ventricular tachycardia unrelated to an acute myocardial infarction. Additionally, the patients had a left ventricular ejection fraction less than 35%, and inducible, sustained, nonsuppressible ventricular tachyarrhythmia on electrophysiologic testing.⁴⁰

During the study, 15 patients in the defibrillator group died vs 39 in the conventional therapy group (P = .009).⁴⁰

MADIT II evaluated the potential survival benefit of a prophylactically implanted defibrillator in the absence of electrophysiologic testing to induce arrhythmias.⁴¹ MADIT II included 1,232 patients with prior myocardial infarctions and a left ventricular ejection fracton of 30% or less. Patients were randomized to receive an implanted cardioverter-defibrillator or conventional medical therapy. The primary end point was death from any cause.⁴¹

The mortality rate was 19.8% in the conventional therapy group vs 14.2% in the defibrillator group (hazard ratio 0.69, P = .016).⁴¹ Thus, MADIT-II confirmed the benefits of prophylactic implantable cardioverter-defibrillator therapy seen in the original MADIT, and additionally eliminated the need for an electrophysiology test prior to device implantation.

SCD-HeFT (the Sudden Cardiac Death in Heart Failure Trial) evaluated whether amiodarone or a conservatively programmed shock-only, single-lead implanted cardioverter-defibrillator would decrease the risk of death (all-cause) in a population with mild to moderate heart failure with ischemic and nonischemic causes.⁴² In this trial, 2,521 patients with an ejection fraction of 35% or less, in NYHA class II or III, and with stable heart failure were randomized to receive a single-chamber implantable cardioverter-defibrillator,  amiodarone, or placebo.

There were 244 deaths in the placebo group, 240 deaths in the amiodarone group (P = .53 compared with placebo), and 182 deaths in the defibrillator group (P = .007 compared with placebo).⁴²

Recommendations. The 2013 ACC/AHA guideline¹ gives implantable defibrillator therapy a class IA recommendation for the primary prevention of sudden cardiac death in selected patients with nonischemic cardiomyopathy or ischemic cardiomyopathy at least 40 days after a myocardial infarction and 90 days after percutaneous coronary intervention or coronary artery bypass grafting; with a left ventricular ejection fraction of 35% or less; and NYHA class II or III symptoms on chronic goal-directed medical management.

This therapy receives a class IB recommendation for primary prevention of sudden cardiac death to reduce total mortality in selected patients at least 40 days after myocardial infarction with a left ventricular ejection fraction of 30% or less and NYHA class I symptoms while receiving goal-directed medical therapy.

Implantable cardioverter-defibrillators are not recommended in patients who otherwise have a life expectancy of less than 1 year.

Devices: Cardiac resynchronization therapy

From 25% to 30% of heart failure patients have an intraventricular conduction abnormality,^43,44 which can result in abnormalities of systolic and diastolic function. Biventricular pacing, in which a pacing lead is placed in the coronary sinus in addition to the right atrium and right ventricle, optimizes synchronization of ventricular contraction.^43,44

MUSTIC (the Multisite Stimulation in Cardiomyopathies study) was a randomized trial designed to assess the efficacy of biventricular pacing (also known as cardiac resynchronization therapy) in heart failure patients.⁴⁴ Entry criteria included NYHA class III heart failure for at least 1 month, left ventricular ejection fraction less than 35%, left ventricular end-diastolic diameter greater than 60 mm, and QRS duration longer than 150 ms. Patients were followed up at 9 and 12 months with 6-minute walking distance, peak oxygen consumption, changes in NYHA class, and left ventricular systolic function by echocardiography or radionuclide testing. Quality of life was assessed by the Minnesota Living With Heart Failure Questionnaire.

At 12 months, patients could walk significantly farther in 6 minutes, and their peak oxygen consumption had increased. They also reported significant improvement in quality of life, and NYHA class improved by 25%. MUSTIC was the first study to show a benefit in exercise tolerance, quality of life, improvement in cardiac performance, and reduction in heart failure symptoms with the use of biventricular pacing at 1 year.

MIRACLE (the Multicenter InSync Randomized Clinical Evaluation) validated the findings seen in MUSTIC by using a larger population size and a double-blinded method.⁴⁵ Compared with a control group, patients who underwent cardiac resynchronization therapy could walk farther in 6 minutes and scored better in NYHA class, quality of life, and left ventricular ejection fraction.⁴⁵

Recommendations. The 2013 ACC/AHA guidelines¹ give cardiac resynchronization therapy a class IA/B indication for NYHA class II, III, or IV patients on goal-directed medical therapy in sinus rhythm with left ventricular ejection fraction 35% or less, left bundle branch block, and QRS duration of 150 ms or more.¹

Devices: Implantable sensors

The future of ambulatory heart failure management may include implantable pulmonary artery pressure sensors.

The CardioMEMS is a permanently implantable pressure measurement system designed to provide daily pulmonary artery pressure measurements in an ambulatory setting with a goal of reducing heart failure-related hospitalizations. Through a transvenous delivery system, an implantable, battery-free sensor is positioned in the distal pulmonary artery.^46,47

CHAMPION (the CardioMEMS Heart Sensor Allows Monitoring of Pressure to Improve Outcomes in NYHA Class III Patients trial) was one of the first major trials to assess the safety and efficacy of implantable pulmonary artery pressure monitoring systems.⁴⁶ The study device was associated with a significant reduction in mean pulmonary artery pressures, fewer heart failure hospitalizations, and better quality of life. The length of stay for heart failure-related hospitalizations was also significantly shorter in the CardioMEMs group.⁴⁶