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"Medical Journeys" is a set of clinical resources reviewed by physicians, meant for the medical team as well as the patients they serve. Each episode of this journey through a disease state contains both a physician guide and a downloadable/printable patient resource. "Medical Journeys" chart a path each step of the way for physicians and patients and provide continual resources and support, as the caregiver team navigates the course of a disease.

Device-based treatments -- whether to mitigate deadly heart rhythms or offload the heart -- have widely variable roles and levels of evidence across the heart failure spectrum.

The best evidence for the widest range of these technologies comes for heart failure with reduced ejection fraction (HFrEF), although only after optimizing guideline-directed medical therapy for some 3 to 6 months to see if left ventricular ejection fraction (LVEF) improves without a device.

The strongest recommendation -- Class I -- in that group is for implantable cardioverter-defibrillators (ICDs) to prevent sudden cardiac death. That includes nonischemic dilated cardiomyopathy or ischemic heart disease at least 40 days post-myocardial infarction, either with LVEF of 35% or less and New York Heart Association (NYHA) class II or III symptoms or with LVEF of 30% or less and NYHA class I symptoms -- both despite a stable regimen of recommended medications.

HFrEF with sinus rhythm left bundle branch block (LBBB) and a QRS duration of at least 150 ms with NYHA class II to ambulatory class IV symptoms also has a strong recommendation for cardiac resynchronization therapy (CRT). More moderate evidence supports consideration of CRT in similar HFrEF patients with a non-LBBB pattern or a QRS duration of 120-149 ms.

CRT is also recommended as reasonable for HFrEF patients with atrial fibrillation if ventricular pacing is needed or can be achieved with atrioventricular nodal ablation or pharmacological rate control and for those getting a new or replacement device who are anticipated to need at least 40% ventricular pacing.

Across the board, those recommendations are only for patients with meaningful survival expected for at least 1 year.

Another type of device therapy that has proven useful for HFrEF patients with severe secondary mitral regurgitation is transcatheter edge-to-edge mitral valve repair (M-TEER).

These devices, of which two systems are now approved (MitraClip and Pascal), are also recommended as reasonable for patients with NYHA II-IV heart failure with severe secondary mitral regurgitation, suitable anatomy, LVEF in the 20-50% range, LV end systolic dimension of 70 mm or less, and pulmonary artery systolic pressure no greater than 70 mm Hg.

Again, a stabilization period of 3-6 months on target or at maximally tolerated guideline-directed medical therapy is needed before a patient is considered a candidate. Also, the multidisciplinary heart team should be involved in M-TEER decisions.

While less commonly used, cardiac contractility modulation devices are approved for NYHA class III HF with an EF of 25% to 45% in patients who are not candidates for CRT. While randomized controlled trials have shown benefits in exercise capacity and quality of life, no mortality or hospitalization benefits have emerged and HF guidelines have not provided a recommendation on their use.

Device-Based Therapy in HFmrEF or HFimpEF

As with the evidence for medical therapy for heart failure with mildly reduced EF in the 41-49% range (HFmrEF) or HF with EF improved to that range (HFimpEF), the evidence for device therapy is scant.

"Strategies for the prevention of sudden cardiac death in patients with EF ≥40% have not been tested," noted a 2022 review on HFmrEF in . The , abandoned after recruitment problems, illustrated the difficulty getting such data.

HF guidelines suggest it's reasonable to consider CRT for patients with high-degree or complete heart block and an LVEF of 36-50%, citing the trial, in which CRT improved outcomes compared with right ventricular pacing alone in patients with LVEF of 50% or less and atrioventricular block.

Guidelines also gave a Class IIa recommendation to ICDs for high-risk patients with arrhythmogenic cardiomyopathy and an LVEF of 45% or greater.

The Nature Reviews Cardiology paper noted that "a growing subgroup" of HFrEF patients who receive an ICD for primary prevention have an improvement in EF by the time of generator replacement and, "therefore, no longer fulfill the criteria for an ICD for primary prevention."

A retrospective with reanalysis of EF at a median 13 months after ICD implantation showed that the mortality benefit from an ICD was similar in patients who improved from below to above 35% EF compared with those whose EF stayed at or below 35%.

"Therefore, the available evidence suggests that the risk of arrhythmia persists at least to some extent in patients with improved or recovered EF," the review noted.

Creating a left-to-right shunt in the interatrial septum to offload the heart has had mixed results in patients with an EF of 40% or greater. In the , the investigational Corvia shunt device did not reduce the total rate of heart failure events or improve health status compared with a sham procedure among patients with pulmonary capillary wedge pressure during exercise of at least 25 mm Hg while exceeding right atrial pressure by at least 5 mm Hg. In the ALLEVIATE-HF early-phase trial program, Alleviant System shunts improved exercise capacity and quality of life.

The RESPONDER-HF sham-controlled study of the Corvia device is , as are trials with . A sham-controlled trial of the Alleviant shunt is planned to (HFpEF) patients specifically.

Device-Based Treatment in HFpEF

The level of evidence isn't strong for device-based therapies in HFpEF yet either.

A on HFpEF in the Journal of the American College of Cardiology noted that rate-adaptive atrial pacing to enhance heart rate responses to exercise in HFpEF patients with chronotropic incompetence did not improve exercise performance or quality of life in the trial. Guidelines don't recommend any cardiac implantable devices for HFpEF.

Results were more promising, albeit preliminary, in the open-label roll-in phase of the testing endovascular splanchnic nerve ablation in HFpEF, showing improved LV filling pressures during exercise and patient-reported health status. Blinded, sham-controlled results will need to confirm its benefit.

The small single-arm trial showed that tricuspid valve TEER improved LV volume at maintained filling pressures. And after a positive testing a device for cardiac contractility modulation, the trial is comparing it to sham.

The 2023 on management of HFpEF summarized the status of these strategies as having benefits that "remain ambiguous," and that "such procedures should be considered only within the context of clinical trials."

Cardiac contractility modulation devices are also being investigated for HFpEF.

Wearables and Remote Monitoring

After the initial diagnosis, continued evaluation of patients outside the office with wearables and remote monitoring devices in an attempt to drive down high event rates has seen some success.

In the , the CardioMEMS implantable pulmonary artery pressure sensor reduced HF hospitalizations by 28% over 6 months in a population of patients with NYHA class III heart failure across the LVEF spectrum who had a prior HF hospital admission.

However, given the trial's nonblinded design and other concerns about bias along with the device's failure in the subsequent GUIDE-HF trial to reduce the composite mortality and total HF events, U.S. guidelines gave the implanted hemodynamic monitor only a 2b recommendation as of uncertain value.

More recently, data released from the randomized added to the clinical picture, showing improved quality of life and reduced heart failure hospitalizations with the CardioMEMS device among patients with moderate-to-severe heart failure versus those treated with contemporary standard of care alone. There was no significant interaction with LVEF above or below the 40% range.

Other noninvasive telemonitoring of physiologics (like physical activity, thoracic impedance, or heart rate) and monitoring via existing implanted cardioverter-defibrillator or cardiac resynchronization therapy devices is not supported by clinical trial evidence, according to the guidelines.

Read previous installments of this series:

Part 1: Heart Failure: A Look at Low Ejection Fraction

Part 2: Exploring Heart Failure With Preserved Ejection Fraction

Part 3: Heart Failure With Reduced Ejection Fraction: Diagnosis and Evaluation

Part 4: Case Study: Lightheadedness, Fatigue in Man With Hypertension

Part 5: Heart Failure With Preserved Ejection Fraction: Diagnosis and Evaluation

Part 6: Heart Failure Medical Management

Part 7: Managing Heart Failure Comorbidities

Part 8: Case Study: Heart Failure Exacerbation Due to an Often Overlooked Cause