Paced rhythms

Sometimes due to damage to the conduction system, or to manage certain types of heart block, it becomes necessary to insert a Permanent Pacemaker (PPM) system. The PPM system consists of one or more electrodes (leads) and a battery (pulse generator). The pulse generator can detect the patient s rhythm and emit an 

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Chamber(s) paced Chambers) sensed Sensing response Rate modulation Multisite pacing 

A=Atrium A = Atrium T=Triggered R=Rate modulation A = Atrium 

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Sgarbossa E, Pinski S, Gates K, Wagner G. Early ECG diagnosis of acute myocardial infarction in the presence ofventricular paced rhythm. Am J Cardiol 1996a 77 423. 

Fig. 12.2 An example of atrial fibrillation (AF) organizing into atrial flutter. A. The upper strip in the top panel demonstrates the atrial electrogram (EGM) and the lower strip demonstrates the annotated markers indicating how the pacemaker classifies each atrial and ventricular event as well as the cycle length (in ms) between each interval. The atrial electrogram shows the rapid irregular atrial rhythm which subsequently transitions into an organized atrial tachycardia. B. Atrial antitachycardia pacing (ATP) therapy - a burst train followed by two premature extrastimuli is delivered restoring atrial paced rhythm. The marker channel notations indicate how the device classifies each beat. Inter-beat intervals are also shown (in ms). AP - atrial paced event VP - ventricular paced event AR - atrial event sensed in atrial refractory period FS - AF sensed event TD - tachycardia detected TS - tachycardia sensed event. Courtesy AM Gillis.

Fig. 16.8 Intermittent pauses in atrial paced rhythm. Atrial pacing is occurring at a rate of about 95 per minute the AR interval (interval between paced P waves [A] and spontaneous QRS complexes [R]) is about 0.33 s. All QRS complexes are spontaneous. There are two longer AA intervals that constitute the intermittent pauses. Applying the shorter AA interval to the pause indicates that it is the QRS complex that is intermittently sensed, inhibiting the atrial output and resetting the atrial escape interval (far-field oversensing). This patient was asymptomatic. The problem was corrected by programming a lower sensitivity.

Fig. 19.16 The Medtronic 9790 programmer generates a uniform amplitude pacemaker spike in response to any high-frequency transient. Although the paced rhythm can be seen in the background, the multiple pacing stimuli are arising from an unknown source extrinsic to the pacemaker and distorted the recording markedly impeding the pacing system evaluation.

When the exercise test is being performed to evaluate concomitant ischemia, it will be necessary to use an ancillary method for evaluating the presence or absence of ischemia as the baseline ECG will be abnormal with a markedly abnormal ST-T wave. In the presence of both a pace rhythm from the RV apex as well as a spontaneous LBBB, there may be septal perfusion abnormalities detected by a thallium scan even in the absence of atherosclerotic coronary artery disease. The abnormal activation sequence will also cause an abnormal contraction pattern that may impair a stress-echo study. 

Totals paced Rhythm Average Rate /mfaiuie... 

Slack JP, Identification of recording artifact in a dual chamber (DDD) paced rhythm, clues from the electrocardiogram, CUn Prog Pacing Electrophysiol 1984 2 384-387. 

Effects on pacemaker thresholds Flecainide increases endocardial pacing thresholds and may suppress ventricular escape rhythms. These effects are reversible. Use with caution in patients with permanent pacemakers or temporary... 

As a result of the weight of evidence for ICD therapy in prevention of SCD in patients with ischemic cardiomyopathy, the American College of Cardiology, American Heart Association, and the North American Society for Pacing and Electrophysiology (now Heart Rhythm Society) revised guidelines for ICD implantation in October 2002... 

Low doses (100-200 mg/d) of amiodarone are effective in maintaining normal sinus rhythm in patients with atrial fibrillation. The drug is effective in the prevention of recurrent ventricular tachycardia. It is not associated with an increase in mortality in patients with coronary artery disease or heart failure. In many centers, the implanted cardioverter-defibrillator (ICD) has succeeded drug therapy as the primary treatment modality for ventricular tachycardia, but amiodarone may be used for ventricular tachycardia as adjuvant therapy to decrease the frequency of uncomfortable cardioverter-defibrillator discharges. The drug increases the pacing and defibrillation threshold and these devices require retesting after a maintenance dose has been achieved. 

Patients with normal sinus rhythm and a wide QRS interval, eg, greater than 120 ms, have impaired synchronization of ventricular contraction. Poor synchronization of left ventricular contraction results in diminished cardiac output. Resynchronization, with left ventricular or biventricular pacing, has been shown to reduce mortality in patients with chronic heart failure who were already receiving optimal medical therapy. 

Drive performance and health processes with the right rhythm to allow the organization to be directed and operated effectively and efficiently. A chemical company can have in place the appropriate review processes, value-drivers, and targets, but not the proper sequence, timing, and pace of performance management events for its particular businesses. 

Arrhthymia— Any abnormal rhythm of the heart, which can be too rapid, too slow, or irregular in pace. 

Kochiadakis GE, Marketou ME, Igoumenidis NE, Chrysostomakis SI, Mavrakis HE, Kaleboubas MD, Vardas PE. Amiodarone, sotalol, or propafenone in atrial fibrillation which is preferred to maintain normal sinus rhythm Pacing CUn Electrophysiol 200023(11 Pt 2) 1883-7. 

Another device that contributes to the rhythm of a line is the caesura, a heavy pause in a line of poetry. Caesuras (indicated by a II mark) may be used to isolate and thus emphasize words or slow the pace. Sometimes they are used to show strong contrasts, as in the following line Before, a joy proposed II behind, a dream. Caesuras may follow punctuation marks such as commas, semicolons, or periods, marks that say slow down to the reader. 

The structure and word choice of the first four lines of the poem also subtly reveal the narrator s attitude toward the lecture, which he finds dry and boring. To emphasize the narrator s emotional uninvolvement with the material. Whitman presents him passively "sitting" (I. 4), the object of the passive verb "was shown" (I. 3). Lines 2, 3, and 4, which describe the lecture, are much longer than the lines in the second stanza, with many caesuras, commas, and semicolons that slow the rhythm and pace (for example, I. 3 ... 

Figure 5. A, Schematic of a Largerdortf perfused rat heart model. Retrograde perfusion is established through the aorta. Perfusate oxygenated with 95% O, and 5% CO, is circulated by a peristaltic pump and the flow can be adjusted. Left ventricular pressure is monitored Ihrough a balloon which is inserted into the empty left ventricle. Heart rhythm is controlled by pacing.

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