Implantable cardioverter defibrillator principle and parameter settings

1 implantable cardioverter defibrillator (ICD) of the basic structure and function

The pulse generator and ICD electrode wires made up of two parts.

Pulse generator's main components including batteries, sensing and pacing lines and capacitors. The battery supplies the energy, the capacitor is charging, discharging, sensing and pacing line is responsible for ECG monitoring, identification of ventricular tachycardia (VT) and ventricular fibrillation (VF) and bradycardia, pacemaker pulse. Early electrode for epicardial electrode, chest after the installation, improved to subcutaneous electrodes, now progress to endocardial electrode by vein, allowing the embedding of greatly simplified. Lead on the one hand, the perception of signals incoming pulse generator, pacemaker signal delivery to the heart. Because of the electrode model, electric shocks through intravenous electrode and finish casing pulse generator or by intravenous endocardial electrode itself.

The basic functionality of ICD is to identify and deal with tachyarrhythmia and bradycardia, their identification and handling of bradycardia works and bradycardia pacemakers are the same.

Here only the identification and treatment of arrhythmia in principle.

1.1 quick arrhythmia recognition

To tachyarrhythmias of heart rate (or its corresponding circumference) and duration (or tachyarrhythmias of cycles) as a basic identification standards, and the initial recognition and identification, the initial identification of standards for each array tachyarrhythmias attack first, and then identify the standards used by the ICD therapy and unterminated tachyarrhythmias judgement.

VT and VF main distinction by frequency. Different manufacturers on the above identification standards of representation, such as the CPI company directly to frequency (times/min) and duration (s), and Medtronic company then the perimeter of the place of the frequency, the number of cardiac cycle that lasts. The following example shows how to identify ICD tachyarrhythmias.

If the recognition criteria set VT is 150 times per minute, and hoped that the VT attack duration is 10 s begin treatment when ICD.

If you use ICD-CPI company Ventak PRx Ⅲ, frequency standards can be directly set to 150 times per minute, the duration is set to 6 s, this is because the duration of the calculation is to meet the frequency standards to start. ICD continuous monitoring process that is, the heart rate of each heart girth and frequency identification standard week looks compare process, when ICD 10 consecutive echocardiography circumference there are eight in judgement is equal to or shorter than the recognition criteria perimeter (frequency standard 150 times per minute, the perimeter is 400 ms) that determine when ICD meet diagnostic criteria for VT and begin computing the duration. Obviously, the calculation of the duration before the tachycardia has lasted for at least 10 cardiac cycle, to the above 150/divided into recognition criteria, 10 4 heart period should as s, so although the duration set to 6 practical s and VT lasted 10 (4 + 6) s. The duration of the start, if 10 cardiac cycle has six meeting frequency identification standard and keep to the end of the duration (in the above example is 6 s), then at the end of the duration of the treatment program, otherwise required to meet the continuous 10 cardiac cycle there are eight in line with the calculation of frequency standards had just begun. Similarly, if you use the Medtronic company's Jewel series products, you need to set frequency standard is 400 ms, duration is 24 cardiac cycle (10 seconds should be 25 cardiac cycle, but is not programmable parameters 25 this value), if 24 cardiac cycle continuous meet the recognition criteria i.e. begin treatment procedures. This kind of ICD's frequency standards and duration are also met; that is, its duration is calculated starting with the CPI company different. About VF duration settings also illustrate. If VF frequency standard developed to 200 times/min, continuous 6 s start treatment, CPI product sets in the same way, i.e. frequency VT 200 times/min, the duration is 3 s (10 cardiac cycle time of occupancy is 3 s); Medtronic products have set the standards to frequency of 300 ms, duration 15/20. The latter means continuous 20 heart period (duration 6 s) 15 can meet the standards set by the frequency that reached the diagnosis of the circumference of the VF of diagnosis only heart rate and duration of the standard, and VT diagnosis in addition to these basic criteria, there is also a secondary standard for use with sinus tachycardia and atrial fibrillation-phase differential. Common ownership tachyarrhythmias of sudden (Onset.

VF diagnostic only heart rate and duration of the standard, and VT diagnosis in addition to these basic criteria, there is also a secondary standard for use with sinus tachycardia and atrial fibrillation-phase differential.

Common ownership tachyarrhythmias of sudden (Onset) and stability (Stability), there is the addition of ICD QRS Group wave width for the identification of VT and supraventricular tachycardia (SVT).

Paroxysmal tachycardia is started with the law of the circumference of the sinus rhythm interphase is relatively short, usually expressed as a percentage.

VT is a sudden outburst of, sinus tachycardia are generally occur gradually, gradually terminated. So the two can be used to identify emergency standards. Unexpected concrete set based on the patients tachycardia arises with the rule of law interval to determine, for example, each time with a heart rate law interval week duration by 25%, you can set its sudden is 20%. Once you have selected the sudden, at the same time meet the initial identification of standards of the heart rate, duration, and the sudden it meet the diagnostic criteria VT.

Stability means tachycardia differences between different Zhou's maximum allowable range, tachycardia, arrhythmia, regularity, usually expressed in milliseconds.

Atrial fibrillation is rapid heart rate, rhythm is not structured, and VT arrhythmia structured or only mildly uneven. Therefore, the identification of both can stability. IfWe observed that both the perimeter while to VT difference not exceeding 30 ms, stability is set to 40-50 ms. After selecting the stability criteria, you must also meet the initial identification of standards of the heart rate, duration and stability to meet the diagnostic criteria VT. If both SVT extra width using the QRS complex standards be differential.

1.2 tachyarrhythmias treat

Arrhythmia treatment with electric shock (Shock) and tachycardia pacing (Antitachycardia pacing, ATP) in two ways.

(1) electric shock: currently electric energy most programmable 0.1 to 34 J.

Product type specific parameter settings, there are certain differences, a small number of products the maximum electric energy of up to 42 j, the majority of products can be continuous shock 6 times. VF and VT can be used this way.

(2) ATP: there are two basic forms, i.e. short array pacing (Burst pacing) and perimeter decrements the pacing (Ramp pacing).

① nonsustained pacing is the same array pacing, perimeter equal and shorter than the tachycardia perimeter of pacing mode. Pacing the set number to perimeter tachycardia perimeter, usually expressed as a percentage of the cardiac cycle perimeter of 75% to 80% of set value, the termination of a higher success rate. Every pacing pulse number according to the treatment effect, pacemaker pulse too few are successful, too much is also not necessary, or even make arrhythmia acceleration. ② perimeter decrements the pacing is the same array pacing, girth gradually shortened pacing mode. This way, the termination of the success rate is higher than the short wave of rapid pacing, but enable arrhythmia accelerated opportunities, pacemaker pulse count more.

VF treatment can only use electric shock.

Generally speaking, the energy of the first electric shock than the test defibrillation threshold high 5 ~ 10 j, starting from the second biggest energy should be used. VT treatment can choose ATP and electric shocks. Electric energy from 0.1 ~ 34 j, generally a lower energy can be effective. ATP can set several programs, each program can choose two pacing mode, but can also be scanned. The so-called scanning refers to when an ATP is invalid, the next time the ATP's pacing perimeter or (and) the law interval automatically according to the set of values. Therefore, the treatment can be VT preferred ATP, invalid for low-power electric cardioversion, then invalid when high energy electric cardioversion of ladder treatment methods.

In addition, ICD is available storage in the electrocardiogram and tachycardia occurs, perimeter, with law interval, treatment time, manner and treatment response, information functions, for follow-up and reasonable adjustments to the diagnosis and treatment procedures.

ICD has electrophysiological function.

With this function you can induce ventricular tachycardia and test the effectiveness of the treatment program.

2 ICD work program settings

2.1 set workspace

According to the patients quickly arrhythmias and treatment set 2 ~ 3 workspace (1 x VF, 1 ~ 2 VT district).

2.2 set tachyarrhythmias of Diagnostics

(1) set each workspace frequency threshold: VF is 200 ~ 250 times/min, VT frequency threshold to clinical attack rate lower than 10 ~ 20 times/hours, two VT district of frequency of at least 20 times per minute.

Further recognition and initial recognition of the same frequency standard.

(2) set the VF and VT duration: VF's initial recognition duration to 3 ~ 5 s for the duration of the VT can be extended accordingly, but generally not more than 10 s; recognition of duration is shorter than the initial recognition.

(3) the sudden, stability criteria: likely sinus tachycardia are standard with sudden, atrial fibrillation history, plus stability standards.

2.3 set quick arrhythmia treatment procedures

(1) VF treatment procedures: VF electric cardioversion area only, the first electric energy ratio defibrillation threshold high 5 ~ 10 j, for security reasons starting from the second largest electric energy use, final 1 ~ 2 times to reverse the polarity of electric shock.

(2) VT treatment procedures: according to ATP-low-energy electric cardioversion-high energy electric cardioversion of ladder treatment settings.

Low frequency VT district can only set the ATP or combined with low energy to electric shocks, high frequency, speed zone can only electric cardioversion, can also be started using a perimeter decrements the pacing of the ATP program. 180/min following VT terminated with ATP's success rate is high, generally with a short array pacing, pacing perimeter from tachycardia perimeter of 80% of each array 4 ~ 10 pulse, sharp decline between 10 ms qualified the minimum perimeter is 200 ms, a total of 4 ~ 6 array. Perimeter decrements the pacing interval usually tachycardia perimeter of 90%, array, array may decline between 5 ~ 10 ms, pacemaker pulse can be fixed or may gradually increase, with lead times of four to six commonly used. Energy program at the ATP, the first energy to 1 ~ 10 J, the second increase of 5 ~ 10 j, the third largest energy available. ATP parameter and set the best of the electric energy to before or during electrophysiologic study results as it was.

2.4 settings on bradycardia pacemakers work parameters.

2.5 settings information stored job parameters (ECG storage power consumption more attention program control instrument tip).

2.6 considerations

① intraoperative measurement of defibrillation threshold, VF terminate the program number of lightning strikes should not be more than 2 times a second time selects the maximum energy.

2 invalid rows should be immediate, in-vitro defibrillation. ② I C D work parameters according to the follow-up of timely adjustments. ③ After each time the program control, verify that the print result set parameters noWrong.