"Лишний" зубец Р? и как его квалифицировать?

[mimoshla]

Да нет. Ни скорость 50 не поможет, ни лупа.
По-Вашему, "конец QT должен вровень с изолинией быть"?

[mimoshla]

Из методички Т.Д.Бутаева "Синдромы удлинённого интервала QT". Скорость 50.
Отравление хлорофосом. Как здесь измерить QT?

[Korzun]

Сообщение от mimoshla

Да нет. Ни скорость 50 не поможет, ни лупа.
По-Вашему, "конец QT должен вровень с изолинией быть"?

У меня зрение давно подорвано книгами и компьютером, так что помимо очков лупой часто пользуюсь для четкости.
Если возвращаться к дефинициям из того же источника, то там это не совсем изолиния, а сегмент ТР.

The problems associated with this measurement include the following: 1) recognizing the onset of the QRS complex and the end of the T wave, 2) determining the appropriate lead(s) in which to measure the QT interval, and 3) adjusting the QT interval for increases in QRS duration, gender, and rate.

...or that the downslope of the T wave be extended by drawing a tangent to the steepest proportion of the downslope until it crosses the TP segment. It should be recognized that defining the end of the T wave in these ways might underestimate the QT interval.

Recommendation

It is recommended that selective subsets of temporally aligned superimposed ECG leads be made available as an optional display to facilitate QT measurement and to validate the onset and end points of the QT interval. In view of the clinical importance of QT-interval prolongation, it is essential to visually validate QT-interval prolongation reported by a computer algorithm.

[mimoshla]

я уже говорила - тема очень сложная.
Как правильно измерять QT - написаны книги. Противоречивые до нельзя.
17 формул для правильного подсчёта интервала QTc. Сами картинки бывают дикими (покажу ещё одну из тех, "что и не снились нашим мудрецам").
У Вас

Сообщение от Korzun

зрение давно подорвано книгами и компьютером

Для beytars, похоже, тема не актуальна.
Мне как-то совсем-совсем не хочется солировать.

[Igor73]

Сообщение от mimoshla

я уже говорила - тема очень сложная.
Как правильно измерять QT - написаны книги. Противоречивые до нельзя.
17 формул для правильного подсчёта интервала QTc. Сами картинки бывают дикими (покажу ещё одну из тех, "что и не снились нашим мудрецам").
У Вас Для beytars, похоже, тема не актуальна.
Мне как-то совсем-совсем не хочется солировать.

Тема удивительно актуальна. В проблеме измерения интервала QT меня поражают две вещи: (1) как мало врачи уделяют этому внимания и (2) как сложно бывает этот QT измерить так, чтобы хотя бы двое врачей совпали в цифрах. Еще эта тема может быть болезненной: мои попытки внедрить в расшифровку ЭКГ рутинное измерение QTc привели к тому, что врач ФД уволился, ну никак не получалось этот QTc измерять:-(

[Igor73]

В виртуальном мире книг и рекомендаций QTc рекомендуют измерять следующим образом:
"How to measure the QT interval
(1) The QT interval should be measured in either lead II or V5-6
(2) Several successive beats should be measured, with the maximum interval taken
(3) Large U waves (> 1mm) that are fused to the T wave should be included in the measurement
(4) Smaller U waves and those that are separate from the T wave should be excluded
(5) The maximum slope intercept method is used to define the end of the T wave (см. картинку)
QT interval with u waves maximum T wave slope intersection
The QT interval is defined from the beginning of the QRS complex to the end of the T wave. The maximum slope intercept method defines the end of the T wave as the intercept between the isoelectric line with the tangent drawn through the maximum down slope of the T wave (left).

When notched T waves are present (right), the QT interval is measured from the beginning of the QRS complex extending to the intersection point between the isoelectric line and the tangent drawn from the maximum down slope of the second notch, T2
Источник - [Ссылки доступны только зарегистрированным пользователям ]

[Igor73]

Но попытка все эти знания применить в реальной жизни не редко заканчивается фиаско по причинам, которые приводит Ирина Николаевна: (1) нисходящее колено зубца Т - это вещь очень не точная, линию провести можно десятком разных способов, (2) зубец U путает все карты

[Igor73]

Сообщение от mimoshla

Да нет. Ни скорость 50 не поможет, ни лупа.
По-Вашему, "конец QT должен вровень с изолинией быть"?

Ирина Николаевна, когда мы плохо видим Р, можно снять ЭКГ по Lewis, можно чреспищеводный зонд поставить и даже эндо-ЭФИ, если уж на то пошло. А нет ли какого-нибудь способа четко рассмотреть окончание Т? Может быть какое-то "хитрое" отведение снять?

[Korzun]

Мнения и книги - это увлекательно, но противоречиво, а документ - это попытка договориться и унифицировать.
Приведу полностью текст документа про QT:

[Ссылки доступны только зарегистрированным пользователям ]
The QT Interval

Measurement of the QT interval and its adjustment for rate, gender, and QRS prolongation represent 2 of the major challenges in electrocardiography. They are matters of great importance to physicians, drug manufacturers, and regulatory agencies because of the relationship between prolongation of the QT interval and potentially lethal ventricular arrhythmias. The document released in October 2005 by the Food and Drug Administration (FDA) provides guidance for the design, conduct, analysis, and interpretation of clinical studies for evaluation of QT-interval prolongation (33).

QT and ST-T patterns vary a great deal in various genotypes of the LQTS. Zhang et al (34) described 10 different ST-T patterns in first 3 genotypes of the syndrome (4 in LQT1, 4 in LQT2, and 2 in LQT3), and these patterns were present in the majority of genotyped LQTS patients.

The QT interval is defined as the interval from the onset of the QRS complex, that is, the earliest indication of ventricular depolarization, to the end of the T wave, that is, the latest indication of ventricular repolarization. The problems associated with this measurement include the following: 1) recognizing the onset of the QRS complex and the end of the T wave, 2) determining the appropriate lead(s) in which to measure the QT interval, and 3) adjusting the QT interval for increases in QRS duration, gender, and rate.

When the majority of ECGs were recorded on single-channel analog machines, various leads were recorded sequentially, and the QT interval was measured manually in the individual leads. Determination of the end of the T wave was often difficult and sometimes impossible, and the onset of the QRS complex and the end of the T wave varied in different leads, appearing shorter when the axis of an individual lead was more perpendicular to the spatial vector of the onset of the QRS complex or the end of the T wave. The onset of the QRS complex tends to occur up to 20 ms earlier in V2and V3than in the limb leads (35). Some regard differences of up to 50 ms in QT intervals measured in the various leads in normal subjects as being normal (36); others have suggested that differences of up to 65 ms were still within the limit of normal (37). This value is reported to be less in women than in men (38).

When the QT interval is measured in individual leads, the lead showing the longest QT should be used (39). This is usually V2 or V3. However, if this measurement differs by more than 40 ms from that in other leads, the measurement may be in error, and measurements from adjacent leads should be considered. If the T wave and U wave are superimposed or cannot be separated, it is recommended that the QT be measured in the leads not showing U waves, often aVR and aVL (39), or that the downslope of the T wave be extended by drawing a tangent to the steepest proportion of the downslope until it crosses the TP segment. It should be recognized that defining the end of the T wave in these ways might underestimate the QT interval.

As detailed in the section on ECG technology (1), most currently used automated digital machines record all leads simultaneously. This technique permits their temporal alignment and superimposition, which facilitates a more accurate assessment of the beginning of the QRS complex, the end of the T wave, and the separation of the U wave from the T wave. As a result, the automatically measured QT interval is often longer than the QT interval as measured in any individual lead, and the values currently regarded as normal, which were established with single-channel sequential recordings, may no longer be valid. Most automated systems do not routinely display the superimposed tracings or the points used to derive the QT interval.

In view of the clinical importance of the QT-interval prolongation, it is essential to visually validate QT-interval prolongation reported by a computer algorithm.

In addition to administration of QT-prolonging cardioactive drugs, a number of conditions can induce QT prolongation. It is often possible to identify a specific cause of QT prolongation when appropriate clinical information is available; for instance, both hypokalemia and hypocalcemia can prolong phase 2 and phase 3 of the action potential and prolong the QT interval. It is not feasible here to compile a comprehensive list of all possible causes of QT prolongation. It is sufficient to emphasize that its presence in an ECG report should call for a careful clinical evaluation of possible causes.
Recommendation

It is recommended that selective subsets of temporally aligned superimposed ECG leads be made available as an optional display to facilitate QT measurement and to validate the onset and end points of the QT interval. In view of the clinical importance of QT-interval prolongation, it is essential to visually validate QT-interval prolongation reported by a computer algorithm.
QT Correction for Rate

Many formulas have been proposed to adjust the QT interval for rate (40, 41). The most widely used is the formula derived by Bazett (42) in 1920 from a graphic plot of measured QT intervals in 39 young subjects. This adjustment procedure divides the measured QT by the square root of the RR interval to derive the rate-adjusted value. The formula introduced by Fridericia (43), also in 1920, uses the cube root of RR. Bazett's formula leaves a strong positive residual correlation (r=0.32) and Fridericia's formula leaves a negative correlation (r=−0.26 to −0.32) with heart rate (44, 45), and the adjusted QT values may be substantially in error, particularly when the heart rate is high. More recently introduced formulas for QT adjustment as a linear or power function of RR or heart rate for adults (44, 45, 46, 47, 48) and for children (49) effectively remove the rate dependence of the adjusted QT, and they are clearly preferable to both Bazett's and Fridericia's formulas. Some investigators have introduced separate normal limits or rate correction factors for each heart rate subinterval using the so-called “bin method” (46, 50).
Recommendation

It is recommended that linear regression functions rather than the Bazett's formula be used for QT-rate correction and that the method used for rate correction be identified in ECG analysis reports. In addition, rate correction of the QT interval should not be attempted when RR interval variability is large, as often occurs with atrial fibrillation, or when identification of the end of the T wave is unreliable.

Продолжение - см. следующий пост.

[Korzun]

Продлжение.

QT Correction for Gender and the Limits for Prolonged and Short QT Interval

Although Bazett's and Fridericia's formulas make no adjustment for gender, many studies have demonstrated that the QT interval is longer in young and middle-aged females than in males. The gender difference is potentially important because women are generally considered to be more prone to malignant arrhythmias in LQTS than men. The gender difference appears during adolescence (51), when the rate-adjusted QT shortens in boys, possibly as a testosterone effect, but undergoes little change in girls.

The reported gender difference in various studies varies from 6 to 10 ms in older age groups and from 12 to 15 ms in younger adults. Overall, the gender difference in rate-adjusted QT interval becomes small after 40 years of age and practically disappears in older men and women. Separate gender- and age-specific QT-adjustment formulas have been proposed to accommodate these differences (21, 44, 46, 47). Normal limits proposed in different studies vary to a certain extent, depending on the characteristics of the study population and particularly on the type of QT-adjustment function used. It is important to recognize that normal limits established using the upper and lower limits of actual percentile distributions of the rate-adjusted QT are preferable to those as mean values ±2×SD because these distributions are strongly skewed (44).

Normal standards for thresholds for abnormal QT from large subgroups of community-based populations are available (21, 44, 45, 46, 47, 48). These limits are relatively uniform in reports that have appropriately used linear regression functions with QT-rate adjustment as a linear or power function of RR or heart rate (21, 44, 46, 47, 48). The following normal limits are suggested as a practical compromise for the evaluation of QT-interval prolongation and shortening in adult men and women: prolonged QT: women, 460 ms or longer; men, longer than 450 ms; and short QT: women and men, 390 ms or shorter.

FDA guidelines for industry recommend that 3 severity levels for rate-corrected QT be reported when considering possible QT-prolonging effects of drugs: longer than 350 ms, longer than 480 ms, and longer than 500 ms (32).

Although the upper normal limits for QT adjusted for rate as a linear function of RR in small groups of children stratified by age, gender, and heart rate have been published (52), the limits for prolonged and short QT established in reasonably large groups of children have been reported only for Bazett's formula (53). In that report, the 98th percentile limit for rate-adjusted QT was approximately 450 ms in children younger than 12 years of age. The gender difference of 8 ms appeared in the 12- to 16-year age group. It should be noted that QT adjusted by Bazett's formula may produce false QT prolongations (45).
Recommendation

It is recommended that, in addition to rate, an adjustment for gender and age be incorporated into QT adjustment. As practical clinical limits for considering the QT interval as abnormal, it is recommended that the adjusted QT of 460 ms or longer in women and 450 ms or longer in men be considered a prolonged QT interval and that QT 390 ms and shorter be considered a short QT interval.
Correction for QRS Duration

The QT interval prolongs in ventricular conduction defects, and an adjustment for QRS duration becomes necessary (54, 55, 56). This can be accomplished best by incorporating QRS duration and RR interval as covariates into the QT-adjustment formula or by using the JT interval (QT duration–QRS duration) (55). If the JT interval is chosen, normal standards established specifically for the JT interval should be used (55).
Recommendation

QT- and JT-adjustment formulas have recently been introduced for use in the setting of prolonged ventricular conduction. With confirmation, they may be incorporated into automated algorithms to provide appropriate correction factors.
Evaluation of QT Intervals in Sequential Tracings

Evaluation of QT intervals from sequential ECG recordings is essential for identification of QT prolongation induced by pharmacological agents in drug studies. It is also helpful as an adjunct to ST analysis in determining the presence of active ischemia in patients suspected of having myocardial infarction.

When sequential tracings from patients recorded at different times of day and at different locations are compared, it is important to recognize that the time of day can influence the QT interval (57, 58), that differences may exist between the different recording systems and between the programs used for QT measurement, and that different formulas for QT-rate adjustment may have been used. Moreover, there is a significant interreader variability in the measurement of QT interval (59). Rigorous standardization of the recording and evaluation procedures should be followed when serial comparison of QT intervals is undertaken.

The FDA guide for industry suggests that in the evaluation of possible QT prolongation induced by drugs, 2 levels of change in serial ECGs in the rate-corrected QT from the baseline be reported: an increase of greater than 30 ms and an increase of greater than 60 ms (33).
Recommendation

It is recommended that for serial comparisons ECG recorders meet specific performance standards and, if possible, be of the same type; that uniform, carefully standardized ECG acquisition and QT-measurement procedures be used; and that, whenever possible, a single reader be responsible for overreading sequential tracings of an individual patient or research subject.
QT Dispersion

Increased heterogeneity of myocardial repolarization may predispose patients to the development of malignant ventricular arrhythmias (60). As indicated above, significant differences exist in the duration of the QT interval when measured in the individual leads. Visualization of these differences is facilitated by the display of a suitable subset of temporally aligned simultaneous leads with a slight separation on the amplitude scale.

The difference between the longest and shortest QT intervals is referred to as QT dispersion. This concept was introduced in 1990 for risk identification in patients with LQTS (61). Since its introduction, QT dispersion has been one of the most popular topics in ECG research. In November 2006, a PubMed search cited 670 publications with QT dispersion in the title, and a Google search under “QT dispersion measurement” revealed 171 000 communications.

The QT-dispersion concept has led to the expectation that QT dispersion is a measure of regional or localized heterogeneity of myocardial repolarization. Numerous studies have suggested an increased risk of morbidity and mortality for an increase in QT dispersion. However, substantial methodological problems with the QT-dispersion measurement have been identified that have raised fundamental questions about the validity of the concept (62, 63, 64, 65). In principle, the expectation that QT dispersion is a measure of the regional or localized heterogeneity of myocardial repolarization implies that the leads with the shortest and longest QT contain signal information at the terminal part of the T wave that is not present in the first 3 orthogonal components of the 12-lead ECG (or the composite global T wave) (65).

Until adequately validated data in specific clinical conditions are presented showing that QT dispersion on the body surface ECG is the counterpart of localized dispersion of myocardial repolarization and conveys adequately strong nondipolar signal information that cannot be extracted from the X,Y,Z components, it seems unwise to include it as a part of the routine ECG report.
Recommendation

It is recommended that QT dispersion not be included in routine ECG reports. However, because of the fundamental importance of the heterogeneity of myocardial repolarization in the genesis of malignant ventricular arrhythmias, continued research into the identification of markers of increased dispersion of myocardial repolarization on the body surface ECG is encouraged.

Т.е. данные документа (договоренностей и унификации) противоречат приведенной Вами, Игорь Петрович, ссылке. [К сожалению. И это только подчеркивает отсутствие единства и сложность унификации.]
На практике QT в большом проценте измеряется без проблем (если измеряется ), а при проблемах я лично буду руководствоваться пусть и не истиной последней инстанции, но унифицированным вариантом договоренностей большинства экспертов.

И про окончание Т в этом документе предлагается неплохой приемчик, который возможен в нашу компьютерную эру. Повторю часть цитаты, т.к. в длинном тексте могла затеряться:
It is recommended that selective subsets of temporally aligned superimposed ECG leads be made available as an optional display to facilitate QT measurement and to validate the onset and end points of the QT interval.

Т.е. усредненная (наложение компьютером отведений друг на друга) ЭКГ пусть лежит рядом при оценке начала и окончания QT.

[mimoshla]

Интересно.
Всё осилила, точнее повторила.

Сообщение от Igor73

Тема удивительно актуальна.

Да, но обойдена вниманием сверху и знанием снизу.

Сообщение от Igor73

А нет ли какого-нибудь способа четко рассмотреть окончание Т? Может быть какое-то "хитрое" отведение снять?

Хорошая идея.

Сообщение от Korzun

Мнения и книги - это увлекательно, но противоречиво, а документ - это попытка договориться и унифицировать.

совершенно согласна! Обожаю порядок и увлекательную книгу.

Сообщение от Korzun

На практике QT в большом проценте измеряется без проблем (если измеряется

Шикарная фраза - измеряется без проблем, если измеряется. Надо запомнить.
И дополнить: Не измеряется с проблемами, если не измеряется.

Сообщение от Korzun

И про окончание Т в этом документе предлагается неплохой приемчик, который возможен в нашу компьютерную эру....
Т.е. усредненная (наложение компьютером отведений друг на друга) ЭКГ пусть лежит рядом при оценке начала и окончания QT.

м-м-м...представляю, что Вы намеряете...

Даже и не знаю, что сказать...Попросить вернуться к недобитой ЭКГ beytars? Так сказать, вооружившись убойными знаниями.
Ведь история начиналась с того, что машина сосчитала удл.QT. Но могучий человеческий мозг сие опроверг.

[mimoshla]

На самом деле - эти роботы способны на многое, глаз да глаз за ними.

[Igor73]

Александр Иванович, вот смотрите, что я прочитал в гайде по интерпретации ЭКГ (часть 4, по Вашей ссылке):
1. Измерение интервала QT и его корректировка на ЧСС, пол и удлинение QRS (расчет QT при блокадах ножек, например) - представляют собой одну из двух непростых задач (challenges можно перевести как "вызов или проблема") в электрокардиографии. Оригинальный текст: "Measurement of the QT interval and its adjustment for rate, gender, and QRS prolongation represent 2 of the major challenges in electrocardiography"
2. Проблемы при измерении связаны с (1) четким определением начала QRS и конца T, (2) определением отведения, в котором измерять QT и (3) корректировка на пол, возраст и ЧСС. Оригинальный текст: "The problems associated with this measurement include the following: 1) recognizing the onset of the QRS complex and the end of the T wave, 2) determining the appropriate lead(s) in which to measure the QT interval, and 3) adjusting the QT interval for increases in QRS duration, gender, and rate."
Дальше эксперты предлагают механизмы решения этой непростой задачи: (1) ориентироваться на наибольший QT (обычно в V2-V3), (2) при наложении U волны искать отведения без нее (обычно aVR/aVL), (3) по нисходящему плечу Т проводить прямую линию и окончанием Т считать пересечение этой линии с ТР и (4) очень просят не доверять компьютерному анализу.
Но из документа очевидно, что измерение QT - это трудная миссия даже для экспертов. Понятно, что эти трудные случаи не такие уж и частые. Особенно эксперты подчеркивают, что QT должен быть точно измерен (с минимальным межэкспертным разбросом) при тестировании препаратов на безопасность, потому что FDA вообще не устраивает все эти +/- 100 мс.
Итого: спасибо за интерес к теме измерения QT. Мне было очень интересно!

[Igor73]

Сообщение от mimoshla

beytars, в Вашем примере хорошо видно, что зубец Т разной морфологии - хорошенький и очень хорошенький. Также видно, что это связано с чсс.
Наверняка на холтере есть и другие варианты Т. Что наводит на мысли об альтернации зубца Т.
По-видимому, есть ещё брадикардия.
Понимаете, куда я клоню.
И присутствует весьма любопытный феномен - интервал QT на разной чсс.

T-Wave Alternans and Arrhythmogenesis in Cardiac Diseases -https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3028203/
Альтернация зубца Т - это очень нехороший признак, потому часто встречается при фатальных аритмиях и может быть предиктором внезапной смерти: описан этот феномен при сердечной недостаточности, LQTS, ишемии миокарда, Бругада. Учитывая возраст пациента, Ирина Николаевна, как я понимаю, намекает на LQTS (брадикардия, отсутствие изменений QT на разной ЧСС).
Так жаль, что Beytars это не интересно..

[Igor73]

С другой стороны, альтернация Т при ХМ - довольно часто встречающийся феномен. На него не только я обратил внимание.
Hashimoto и соавт. анализировали TWA у здоровых добровольцев и показали, что этот феномен не редкость при ХМ у здоровых людей, кроме того TWA зависит от ЧСС
Ссылка - [Ссылки доступны только зарегистрированным пользователям ]
В идеале - снять 12-канальную ЭКГ в покое, собрать семейный анамнез, может даже зарегистрировать ЭКГ у родственников 1-й линии. Разбираться, вообщем..