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In the course of worsening heart failure, some hearts will incur damage to the specialized heart cells that carry signals needed for proper contraction. When this causes the signals to travel out of sync, the pumping becomes less forceful and efficient. This knowledge has spurred the development of devices for "biventricular pacing."
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Standard implanted pacemakers are equipped with two wires (or "leads") that conduct pacing signals to specific regions of the heart (usually at positions A and C). The biventricular pacing devices have added a third lead (to position B) that is designed to conduct signals directly into the left ventricle. The combination of all three leads creates a synchronized pumping of the ventricles, increasing the efficiency of each beat and pumping more blood on the whole. |
Since only 15 to 25% of heart failure patients will have the specific conditions that would warrant implantation of a biventricular pacer, this resynchronization device will not replace most standard heart failure treatments and medications.
COMPANION Protocol - This was a study of Biventricular Pacing with pacemaker or pacemaker-defibrillator in the treatment of more than 1000 patients with advanced heart failure.
Heart failure patients with symptoms including shortness of breath and fatigue on optimal medical management, received either
- Optimal medical management alone,
- Optimal medical management and biventricular pacing therapy
- Optimal medical management and biventricular pacing therapy with automatic cardiac defibrillator.
The 3 year trial results indicated a significant reduction in mortality and hospitalization for patients who received either CRT (cardiac resynchronization therapy otherwise referred to as biventricular pacing) or both CRT and a defibrillator (CRT-D) over the patients who received only optimal pharmaceutical therapy (OPT). Some results published are reflected in this chart:
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12-Month Outcomes
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OPT
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CRT
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CRT-D
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Primary endpoint (combined all-cause mortality or all-cause hospitalization)
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68%
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55%
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56%
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Combined all-cause mortality or heart failure hospitalization
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45%
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30%
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28%
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All-cause mortality
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19%
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14%
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12%
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*Chart taken from http://www.medscape.com/viewarticle/451768
These results apply to individuals with:
- Persistent symptoms of heart failure, as result of left ventricular systolic dysfunction.
- Low ejection fraction,
- Delayed electrical activation of the heart (prolonged QRS on ECG).
For these patients, the results from this and other studies demonstrate that mortality is reduced significantly by CRT and reduced even more by both CRT and a defibrillator. CRT alone seems to be a major factor in the decline in hospitalization.
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