Pacemaker Timing Part I Pacemaker Timing Objectives z

Pacemaker Timing Part I

Pacemaker Timing

Objectives: z. Describe expected pacemaker function based on the NBG code z. Interpret intervals comprisingle and dual chamber timing z. Recognize various modes of dual chamber device operation from lower to upper rate behaviors z. Calculate upper rate behavior based on programmed parameters z. Identify therapy specific device operations when presented on patient ECG

Timing Intervals Are Expressed in Milliseconds z. One millisecond = 1 / 1, 000 of a second

Converting Rates to Intervals and Vice Versa z. Rate to interval (ms): – 60, 000/rate (in bpm) = interval (in milliseconds) – Example: 60, 000/100 bpm = 600 milliseconds z. Interval to rate (bpm): – 60, 000/interval (in milliseconds) = rate (bpm) – Example: 60, 000/500 ms = 120 bpm

NBG Code Review I Chamber Paced II Chamber Sensed III Response to Sensing V: Ventricle T: Triggered P: Simple programmable P: Pace A: Atrium I: Inhibited M: Multiprogrammable S: Shock D: Dual (A+V) D: Dual (T+I) C: Communicating D: Dual (P+S) O: None R: Rate modulating O: None S: Single (A or V) O: None IV Programmable Functions/Rate Modulation O: None V Antitachy Function(s)

Single-Chamber Timing

Single Chamber Timing Terminology z. Lower rate z. Refractory period z. Blanking period z. Upper rate

Lower Rate Interval z. Defines the lowest rate the pacemaker will pace Lower Rate Interval VP VP VVI / 60

Refractory Period z. Interval initiated by a paced or sensed event z. Designed to prevent inhibition by cardiac or non -cardiac events Lower Rate Interval VP Refractory Period VP VVI / 60

Blanking Period z. The first portion of the refractory period z. Pacemaker is “blind” to any activity z. Designed to prevent oversensing pacing stimulus Lower Rate Interval VP Blanking Period Refractory Period VP VVI / 60

Upper Sensor Rate Interval z. Defines the shortest interval (highest rate) the pacemaker can pace as dictated by the sensor (AAIR, VVIR modes) Lower Rate Interval Upper Sensor Rate Interval VP Blanking Period Refractory Period VP VVIR / 60 / 120

Single Chamber Mode Examples

VOO Mode z. Asynchronous pacing delivers output regardless of intrinsic activity Lower Rate Interval VP Blanking Period VOO / 60 VP

VVI Mode z. Pacing inhibited with intrinsic activity Lower Rate Interval { VP Blanking/Refractory VVI / 60 VS VP

VVIR z. Pacing at the sensor-indicated rate Lower Rate Upper Rate Interval (Maximum Sensor Rate) VP VP Refractory/Blanking VVIR / 60/120 Rate Responsive Pacing at the Upper Sensor Rate

AAIR z. Atrial-based pacing allows the normal A-V activation sequence to occur Lower Rate Interval Upper Rate Interval (maximum sensor rate) AP Refractory/Blanking AAIR / 60 / 120 (No Activity) AP

Other Single Chamber Operations

Hysteresis z. Allows the rate to fall below the programmed lower rate following an intrinsic beat Lower Rate Interval-60 ppm VP VP Hysteresis Rate-50 ppm VS VP

Noise Reversion z. Continuous refractory sensing will cause pacing at the lower or sensor driven rate Lower Rate Interval Noise Sensed VP VVI/60 SR SR VP

Dual-Chamber Timing

Benefits of Dual Chamber Pacing z. Provides AV synchrony z. Lower incidence of atrial fibrillation z. Lower risk of systemic embolism and stroke z. Lower incidence of new congestive heart failure z. Lower mortality and higher survival rates

Benefits of Dual-Chamber Pacing Study Results Higano et al. 1990 Improved cardiac index during low level exercise (where most patient activity occurs) Gallik et al. 1994 Increase in LV filling Santini et al. 1991 30% increase in resting cardiac output Rosenqvist et al. 1991 Decrease in pulmonary wedge pressure Increase in resting cardiac output Sulke et al. 1992 Increase in resting cardiac output, especially in patients with poor LV function Decreased incidence of mitral and tricuspid valve regurgitation

Four “Faces” of Dual Chamber Pacing z. Atrial Pace, Ventricular Pace (AP/VP) AV AP V-A VP Rate = 60 bpm / 1000 ms A-A = 1000 ms AV AP VP V-A

Four “Faces” of Dual Chamber Pacing z. Atrial Pace, Ventricular Sense (AP/VS) AV AP V-A VS Rate = 60 ppm / 1000 ms A-A = 1000 ms AV AP VS V-A

Four “Faces” of Dual Chamber Pacing z. Atrial Sense, Ventricular Pace (AS/ VP) AV AS VP V-A AV AS Rate (sinus driven) = 70 bpm / 857 ms A-A = 857 ms VP

Four “Faces” of Dual Chamber Pacing z. Atrial Sense, Ventricular Sense (AS/VS) AV AS V-A VS Rate (sinus driven) = 70 bpm / 857 ms Spontaneous conduction at 150 ms A-A = 857 ms AV AS VS V-A

Dual Chamber Timing Parameters z. Lower rate z. AV and VA intervals z. Upper rate intervals z. Refractory periods z. Blanking periods

Lower Rate z. The lowest rate the pacemaker will pace the atrium in the absence of intrinsic atrial events Lower Rate Interval AP DDD 60 / 120 VP AP VP

AV Intervals z. Initiated by a paced or non-refractory sensed atrial event – Separately programmable AV intervals – SAV /PAV Lower Rate Interval PAV 200 ms AP DDD 60 / 120 VP SAV 170 ms AS VP

Atrial Escape Interval (V-A Interval) Lower rate interval – AV interval V-A interval

Atrial Escape Interval (V-A Interval) z. The interval initiated by a paced or sensed ventricular event to the next atrial event Lower Rate Interval 200 ms AV Interval AP DDD 60 / 120 PAV 200 ms; V-A 800 ms VP 800 ms VA Interval AP VP

Upper Activity (Sensor) Rate z. In rate responsive modes, the Upper Activity Rate provides the limit for sensor-indicated pacing Lower Rate Limit Upper Activity Rate Limit PAV DDDR 60 / 120 A-A = 500 ms AP VP V-A PAV AP VP V-A

Upper Tracking Rate z. The maximum rate the ventricle can be paced in response to sensed atrial events Lower Rate Interval { Upper Tracking Rate Limit SAV AS VA VP DDDR 60 / 100 (upper tracking rate) Sinus rate: 100 bpm SAV AS VP VA

Refractory Periods z. VRP and PVARP are initiated by sensed or paced ventricular events – The VRP is intended to prevent self-inhibition such as sensing of T-waves – The PVARP is intended primarily to prevent sensing of retrograde P waves A-V Interval (Atrial Refractory) Ventricular Refractory Period (VRP) AP Post Ventricular Atrial Refractory Period (PVARP) VP

Blanking Periods z. First portion of the refractory period-sensing is disabled AP AP VP Atrial Blanking (Nonprogrammable) Post Ventricular Atrial Blanking (PVAB) Post Atrial Ventricular Blanking (Nonprogrammable)

General Medtronic Pacemaker Disclaimer INDICATIONS Medtronic pacemakers are indicated for rate adaptive pacing in patients who may benefit from increased pacing rates concurrent with increases in activity ( Thera, Thera-i, Prodigy, Preva and Medtronic. Kappa 700 Series) or increases in activity and/or minute ventilation (Medtronic. Kappa 400 Series). Medtronic pacemakers are also indicated for dual chamber and atrial tracking modes in patients who may benefit from maintenance of AV synchrony. Dual chamber modes are specifically indicated for treatment of conduction disorders that require restoration of both rate and AV synchrony, which include various degrees of AV block to maintain the atrial contribution to cardiac output and VVI intolerance (e. g. , pacemaker syndrome) in the presence of persistent sinus rhythm. 9790 Programmer The Medtronic 9790 Programmers are portable, microprocessor based instruments used to program Medtronic implantable devices. 9462 The Model 9462 Remote Assistant™ is intended for use in combination with a Medtronic implantable pacemaker with Remote Assistant diagnostic capabilities. CONTRAINDICATIONS Medtronic pacemakers are contraindicated for the following applications: · Dual chamber atrial pacing in patients with chronic refractory atrial tachyarrhythmias. · Asynchronous pacing in the presence (or likelihood) of competitive paced and intrinsic rhythms. · Unipolar pacing for patients with an implanted cardioverter-defibrillator because it may cause unwanted delivery or inhibition of ICD therapy. · Medtronic. Kappa 400 Series pacemakers are contraindicated for use with epicardial leads and with abdominal implantation. WARNINGS/PRECAUTIONS Pacemaker patients should avoid sources of magnetic resonance imaging, diathermy, high sources of radiation, electrosurgical cautery, external defibrillation, lithotripsy, and radiofrequency ablation to avoid electrical reset of the device, inappropriate sensing and/or therapy. 9462 Operation of the Model 9462 Remote Assistant™ Cardiac Monitor near sources of electromagnetic interference, such as cellular phones, computer monitors, etc. may adversely affect the performance of this device. See the appropriate technical manual for detailed information regarding indications, contraindications, warnings, and precautions. Caution: Federal law (U. S. A. ) restricts this device to sale by or on the order of a physician.

Medtronic Leads For Indications, Contraindications, Warnings, and Precautions for Medtronic Leads, please refer to the appropriate Leads Technical Manual or call your local Medtronic Representative. Caution: Federal law restricts this device to sale by or on the order of a Physician. Note: This presentation is provided for general educational purposes only and should not be considered the exclusive source for this type of information. At all times, it is the professional responsibility of the practitioner to exercise independent clinical judgment in a particular situation.

Continued in Pacemaker Timing Parts II and III