RU2261124C2 - Method for estimating electric properties of working myocardium - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: method involves recording conduction time from St2-A2 or St2-V2 intervals at each electrostimulation stage. Working myocardium refraction index is calculated by using distance between distal and proximal electrode poles relative and effective refraction period of atrium and ventricles and intra-atrial and intraventricular conduction speeds. Electric state of myocardium is evaluated from refraction index value.

EFFECT: high accuracy of estimation.

5 dwg, 1 tbl

Description

The invention relates to medicine, namely to cardiology and arrhythmology, and can be used to diagnose cardiac arrhythmias, as well as the functional state of the myocardium in children and adults.

A known method for assessing the electrical properties of a working myocardium, based on the registration of its conductivity and refractoriness in the process of electrophysiological studies (EFI) [1, 2].

In the cavity of the right atrium or right ventricle, a multi-contact diagnostic electrode is performed. Electrostimulation (ES) is performed from the distal poles of the electrode, and electrograms (EG) are recorded from the proximal poles: potentials A - along the atrial canal and V - along the ventricular. To determine the atrial (intraventricular) conduction, asynchronous electrical stimulation of the atrium (ventricle) is performed with a frequency of 10 pulses per minute higher than the frequency of the spontaneous rhythm. The interval from the pace of the pacemaker to the atrial (ventricular) potential is the time of the intraatrial (intraventricular) conduction. However, this method characterizes the conductivity of the myocardium without regard to the refractory state in which it is located.

By programmed pacing, the numerical values of the boundaries of various states of myocardial refractivity are determined: relative, effective and functional refractory periods. However, this method does not take into account the speed of conducting in different periods of refractoriness.

Thus, there is no way to dynamically evaluate the rate of deceleration of the myocardium in its various refractory states.

The aim of this invention is to improve the accuracy of the electrophysiological diagnosis of the condition of the working myocardium.

This goal is achieved by the fact that with the help of diagnostic pacing, the refractivity indices are measured, the value of which is used to judge the change in conductivity in a different refractory state of the myocardium. The refractoriness index is a dynamic indicator and shows the degree of deceleration of the myocardial velocity when scanning relative myocardial refractoriness. To determine it, it is necessary to divide the range of changes in the time of conducting (VP) by the duration of such a change. Thus, the scanning period is the difference between the relative and effective refractory periods, that is, the interval in which the slowdown occurs until the myocardium ceases to be excited. Given the fact that the distance between the contacts of the electrode can be different, the VP must be compared with the length of the studied area and determine the absolute speed (in m / s).

Thus,

IR - refractoriness index,

V _max - maximum speed,

V _min - the minimum speed,

L is the distance between the proximal and distal poles (mm),

VP _max - maximum time (ms),

VP _min - the minimum time (ms),

ORP - relative refractory period (ms),

ERP - effective refractory period (ms).

To convert to units of measurement (mm / s / ms), the numerator is multiplied by 1000.

So, in accordance with the formula, the value of the refractivity index 4.2 shows that during a programmed ES with a decrease in the extrastimulus delay by 1 ms, the myocardial velocity slows down by 4.2 mm / s.

The method is as follows:

To assess the electrical properties of the working myocardium, a multi-contact diagnostic electrode is used, which is installed to the atrium or ventricle from the side of the endocardium (with emergency EPI) or the epicardium (with epicardial EPI);

through distal contacts, a programmed ES is carried out with a base frequency of 10 pulses per minute higher than the spontaneous frequency, and a sequential decrease in the delay of the extra stimulus;

during electrical stimulation, a surface electrocardiogram and electrograms from proximal contacts are continuously recorded on the monitor of the electrophysiological complex;

at each step of electrical stimulation, the interval St2-A2 is measured for atrial ES (intracardiac conduction, runway) or St2-V2 for ventricular ES (intraventricular conduction, intraventricular conduction);

measure the effective and relative refractory periods of the atria (ventricles). For the relative refractory period of the atrium (ORPP) take the maximum value of St1-St2, at which there is an extension of the interval St2-A2 on the electrogram (figure 1). For the effective refractory period of the atrium (ERP), the maximum value of St1-St2 is taken, at which there is no atrial electrical activity behind the test spike (Fig. 2). For the relative refractory period of the ventricle (ARV) take the maximum value of St1-St2, at which there is an extension of the interval St2-V2 on the electrogram (figure 3). For the effective refractory period of the ventricle (ERP), the maximum value of St1-St2 is taken, at which there is no ventricular electrical activity behind the test spike (Fig. 4);

calculate the indices of refractoriness (IR) of the working myocardium according to the formulas

IRp - atrial myocardial refractivity index (mm / s x ms),

L is the distance between the distal and proximal poles of the electrode (mm),

ORPP - the relative refractory period of the atria (ms) (Fig. 5, A),

ERP - effective atrial refractory period (ms) (Fig. 5, B),

Runway _max - maximum atrial conduction speed (ms) (Fig. 5, B),

Runway _min - minimum atrial conduction speed (ms) (Fig. 5, G),

IRzh - ventricular myocardial refractivity index (mm / s x ms),

PCA - the relative refractory period of the ventricles (ms),

ERP - effective ventricular refractory period (ms),

VZhP _max - the maximum speed of intraventricular conduction (ms),

VZhP _min - the minimum rate of intraventricular conduction (ms).

The application of the method is illustrated by the following example.

Example. Patient B-ko, 47 years old. Operated in a clinic in 2002 for mitral defect. Mitral valve and tricuspid valve prosthetics according to De Vega were performed. After thoracotomy and opening of the pericardial cavity, the 6-pin electrode wire is installed on the epicardial surface of the left atrium and right atrium. The distance between the distal and proximal contacts is 40 mm. The main indicators are measured (tab.).

Table Options Right atrium Left atrium PPR, ms 210 250 ERP, ms 160 160 Runway _max , ms 145 167 Runway _min , ms 96 109

Refractivity indices were calculated using the formulas above:

Thus, it was revealed that when scanning the relative refractory period, the speed of conducting in the right atrium decreased twice as intensively than in the left atrium.

In the postoperative period, the patient repeatedly experienced paroxysms of atrial flutter, which were stopped medically. It is known that the pathogenesis of a typical form of atrial flutter is based on the deterioration of the electrophysiological state of the myocardium of the right atrium. Thus, in contrast to the values of ORP, ERP, runway _max and runway _min, it was the refractoriness index that showed qualitative changes in the right atrium and was a more sensitive prognostic characteristic than myocardial refractoriness and conductivity.

The method described above allows to qualitatively and quantitatively evaluate the electrical state of the working myocardium in patients with any cardiac pathology, regardless of the age and size of the heart.

Literature:

1. Josephson M.E. Clinical cardiac electrophysiology: Techniques and interpretations. - Philadelphia: Lea & Febiger, 2002 .-- P.456.

2. Greenspan A.M., Camardo J.S., Horowitz L.N. et al. Human ventricular refractoriness: effects of increasing current.- Am. J. Cardiology, N 47, 1981. - P.244.

Claims (1)

A method for assessing the electrical properties of a working myocardium, including determining the conductivity and refractoriness of a working myocardium, characterized in that a multi-contact electrode is installed on the epicardial or endocardial surface of the atria or ventricles of the heart, programmed electrical stimulation is carried out from the distal contacts of the electrode, and time is recorded at each stage of electrical stimulation from proximal contacts at intervals of ₂ St St ₂ or -A ₂ -V _2, whereupon counting refractivity index p bochego myocardium using the formulas Irp = | 1000 × L × (runway min-runway max) / runway max × runway min × (ORPT-ERPP) |; Irzh = | 1000 × L × (ВЖПmin-ВЖПmax) / (ВЖПmax × ВЖПmin × (ОПЖ-ЭРЖ) |, where IRP is the atrial myocardial refractivity index (mm / s × ms); L is the distance between the distal and proximal poles of the electrode (mm); ORPP - relative atrial refractory period (ms); ERP - effective atrial refractory period (ms); VPPmax - maximum atrial conduction velocity (ms); BPPmin - minimum rate of atrial conduction (ms); Irzh - ventricular myocardial reactivity index (mm / s × ms); PCA - the relative refractory period of the ventricles (ms); ERP - effective ventricular refractory period (ms); VZhPmax - maximum rate of intraventricular conduction (ms); VZhPmin - the minimum rate of intraventricular conduction (ms), and the electrical state of the myocardium is assessed by the value of the refractivity index.

Images