Paced Rhythms

Paced Rhythms Rate: Determined by Pacemaker PRI: <.20 QRS: Variable based on type of pacer Rhythm: Regular Source of pacer: Pacemaker Characteristics: Device that substitutes for the normal pacemaker of the heart’s electrical conduction system; Generator-controls rate & strength of each electrical impulse, Lead wires-electrode at the tip relay the electrical impulse from the generator to the myocardium. Types: Temporary: used to sustain HR in an emergency situation: Transcutaneous (TCP)-external cardiac pacing, Transvenous-lead wire threaded through the skin into a large vein Indications: Suppression of ectopic atrial or ventricular rhythm, Acute MI with symptomatic bradycardia, 2nd & 3rd degree AV block or bundle branch block, Maintenance of adequate HR during special procedures or as prophylaxis after an open heart surgery, Termination of AV nodal reentry Permanent: implanted in patient’s chest Indications: Chronic atrial fibrillation with slow ventricular response, Fibrotic or sclerotic changes in the cardiac conduction system, Sick sinus syndrome or Sinus node dysfunction, Tachyarrhythmias, Symptomatic bradycardia and Third degree AV block not responding to pharmacologic interventions. Atrial: lead wire inserted into the Right atrium-stimulates the atrium then travels down the electrical conduction through the ventricles. Automatic interval Ventricular: lead wire inserted into the Right ventricle. The electrical impulse from the pacemaker generator produces ventricular depolarization Automatic interval AV sequential: two electrodes on the lead wire one placed on the R atrium & one on the R ventricle. Artificial impulses stimulate or pace first the atria, then the ventricles Atrial Automatic Interval Ventricular Automatic Interval Rules for interpretation of Pacemaker Rhythms: Same as for dysrhythmias, Remember: Properly functioning pacemakers will produce rhythms with pacemaker spikes. Spikes indicates only that the pacemaker is firing. They do not reveal information relative to ventricular contraction. Assess your patient for presence of symptoms. Identify patient’s own rhythm and rate, Identify the pacemaker rate - Measured pacer spike to pacer spike, What type of complex does the spike produce? -P waves - QRS waves, Does every pacemaker spike produce a complex? (capture), Is the pacer sensing the patient’s rhythm correctly? Code System: 1st letter: chamber being paced A-atrium V-ventricle D-dual (both) 3rd letter: type of response by pacemaker to sensory I-Inhibited (pacemaker will not function when the person’s heart beats O-none T-triggered D-dual 5th letter: ability of generator to defibrillate P-Antitachycardia S-Shock D-antitachycardia processing & shock O-none 2nd letter: chamber sensed A-atrium V-ventricle D-dual (both O-off th 4 letter: ability of generator to be programmed O-none P-Simple programmability M-Multi programmability C-Telemetry ability P-ability of rate to change with activity Common Problems associated with Pacemakers: Battery failure - Decreased amplitude of pacemaker spike and a slowing pacemaker rate. Pacemaker batteries will not run out unexpectedly. When a battery is running low, the elective replacement indicator (ERI) is activated. Physicians can detect this activation during a routine office visit. In addition, the battery status and the general functioning of the pacemaker can be tested over the telephone. This is generally done every one to two months. Pacemakers will continue to function for approximately six months after the ERI is activated, allowing ample time to schedule an elective replacement procedure. Runaway Pacemakers - Rapid rate of electrical impulse discharge results. This potentially life-threatening malfunction of older-generation pacemakers is related to low battery voltage (e.g. overdue pacemaker replacement). The pacemaker delivers paroxysms of pacing spikes at 2000 bpm, which may provoke ventricular fibrillation. Paradoxically, there may be failure to capture — causing bradycardia — because the pacing spikes are very low in amplitude (due to the depleted battery voltage) and because at very high rates the ventricle may become refractory to stimulation. Application of a magnet can be lifesaving but definitive treatment requires replacement of the pacemaker. Failure to sense: Pacemaker fails to sense the patient's own intrinsic rhythm and generates a pacer spike in the intrinsic rhythm's own QRS, absolute or relative refractory period of the T wave. The ventricular capture following the pacer spike may or may not occur. This can cause lethal arrhythmia. Failure to sense can be caused when the sensitivity setting is too low. EKG Characteristics: Rate: It may be regular or irregular. Rhythm: It can be any intrinsic rhythm in which the pacemaker spike is in the QRS, absolute, or relative refractory period of the T wave. QRS complex: It is within the normal limits of the intrinsic rhythm. Nursing Priorities & Potential Treatments: Obtain the blood pressure, pulse, respiratory rate, O2 saturation and notify the MD. Closely observe for ventricular tachycardia caused by failure to sense. Failure to Capture: Failure to capture of a pacemaker happens when the output is too low, resulting in a failure to depolarize the ventricle, which causes an absence of a mechanical contraction of the ventricle, or no QRS. It can occasionally happen or be constantly happening which results in ventricular standstill and a pulseless patient. EKG Characteristics: Rate: It will be irregular due to the failure to produce QRS. Rhythm: The pacemaker spike or spikes will not have a QRS following them. P Wave: It may be absent or present. QRS Complex: A loss of a QRS behind a pacer spike. Nursing Priorities & Potential Treatments: Should the loss to capture be occasional, one should get a blood pressure, pulse rate, respiration rate, and O2 saturation. This is to determine if the patient is tolerating the failure to capture. If the failure to capture is continuous, the patient will be pulseless or have a symptomatic bradycardia. This can range from a situation in which medication may be needed, or a code situation in which one would follow hospital protocol. External pacing may be an option for this patient Failure to Fire (Pace): In failure to fire or pace, the patient’s rhythm returns to whatever rhythm the patient had prior to receiving a pacemaker. EKG Characteristics: By definition this occurs when the pacemaker fails to create pacemaker spikes or it creates fewer than the preset number of pacemaker spikes per minute. Nursing Priorities & Potential Treatments: When the patient returns to his pre-pacemaker rhythm, he will have a return of his pre-pacemaker symptoms as well. Like all bradycardic patients he will have hypotension, possibly syncope or near syncope and chest pain. His pre-pacemaker rhythm may also be asystole. In which case the patient will require emergent transcutaneous pacemaker, possibly CPR and a code called. Under sensing: In under sensing, a pacemaker spike will occur too soon after an intrinsic complex. This occurs because the pacemaker did not see or sense the intrinsic beat. When a pacemaker sees an intrinsic QRS or P wave it should inhibit and not fire. The pacemaker should also reset its timer to the preset automatic interval to watch for the next intrinsic complex. If the pacemaker does not see another intrinsic complex by the time its automatic interval timer is completed, the pacemaker will fire. Remember a pacer spike tells you the pacemaker fired. In under sensing, you will see pacemaker spikes closer to the intrinsic complex than expected. When it fires too soon, the pacemaker is under sensing. You will use the automatic interval to determine if the pacemaker is firing too soon. EKG Characteristics: Rate: Pacer spike occurs too soon after intrinsic complex. Extra spikes on EKG that are early. Extra spikes may come in the middle of a P wave, QRS, or T wave Nursing Priorities & Potential Treatments: Palpitations, Should the under sensing be occasional, one should get a blood pressure, pulse rate, respiration rate, and O2 saturation. This is to determine if the patient is tolerating the under sensing. If the under sensing is continuous, the patient will be pulseless or have a symptomatic bradycardia. This can range from a situation in which medication may be needed, or a code situation in which one would follow hospital protocol. External pacing may be an option for this patient Over sensing: In over sensing, a pacemaker spike will not occur when expected. We would expect the pacemaker to fire following its automatic interval when an intrinsic complex does not occur. If the pacemaker does not see an intrinsic complex by the time its automatic interval timer is completed, the pacemaker should fire. Prior to completion of the second automatic interval, an intrinsic complex occurred so the pacemaker appropriately inhibited and reset it’s automatic interval at the peak of the QRS. EKG Characteristics: Pacer misinterprets other electrical activity as a QRS, Pacer fires at a rate slower than the preset rate, Pacer does not fire when expected, Pacemaker spikes appear further away from intrinsic or paced complexes than expected based on the automatic interval Nursing Priorities & Potential Treatments: Bradycardia, hypotension, Dizziness, syncope, diaphoresis, & Chest pain. Since the pacemaker is firing less than expected, the patient will have a return of symptoms that lead to pacemaker insertion. Remember in under sensing we said you would see over pacing. In over sensing you will see under pacing. You will expect the pacemaker to produce a pacer spike and it does not Pacemaker Summary Pacer Spikes Atrial Pacing Ventricular Pacing AV Pacing Loss of Capture Failure to Pace Over Sensing Under Sensing In front of P wave In front of QRS In front of both P wave & QRS No pacer spikes One pacer spike per P wave One pacer spike per QRS One or Two pacer spikes per PQRST complex Pacer spike not followed by a complex Pacer spikes not occurring as expectedtoo far away from intrinsic complexes Pacer spikes too close to intrinsic complex