1. Higher Output Voltage = Increased Energy Consumption

• Energy per Pulse: Each time the pacemaker delivers an electrical impulse, the energy expended is directly related to the output voltage and pulse duration. A 2.5V setting delivers more energy with each pulse compared to lower voltage settings.
• Mathematical Relationship: According to Ohm's Law, a higher voltage leads to higher current draw I = V/R, resulting in significantly more power consumption P = VI = V²/R per pulse.

2. Pacing Burden (Even at 50 bpm)

• Continuous Pacing: If the patient's intrinsic heart rhythm is consistently below 50 bpm, the pacemaker will pace 100% of the time.
• Cumulative Effect: Even at a relatively low rate of 50 bpm, this translates to approximately 26,280,000 pulses per year (50 beats/minute × 60 minutes/hour × 24 hours/day × 365 days/year).
• Energy Accumulation: The energy consumed by millions of pulses adds up significantly over time, accelerating battery depletion.

3. Synergistic Effect

• Multiplicative Impact: The combination of higher output voltage and high pacing burden creates a multiplicative effect on battery drain—each energy-intensive pulse is delivered frequently.
• Quadratic Relationship: Since power consumption is proportional to the square of voltage (V²), even a modest increase in voltage significantly increases energy use per pulse.

4. Additional Contributing Factors

• Initial Projection Assumptions: The original 15-year projection was likely based on nominal programming parameters and assumed less frequent pacing (not 100% pacing).
• Pacing Threshold Changes: The heart tissue at the electrode site may require higher voltage to consistently capture and initiate heartbeats, necessitating the 2.5V setting.
• Pulse Width: If the pulse width (duration of each electrical impulse) was also increased, this would further increase energy consumption per pulse.