25 research outputs found
Evolution of left ventricular strain after a first time myocardial infarction. A study using velocity encoded magnetic resonance imaging
Longitudinal strain from velocity encoded cardiovascular magnetic resonance: a validation study
Longitudinal shortening remains the principal component of left ventricular pumping in patients with chronic myocardial infarction even when the absolute atrioventricular plane displacement is decreased
Magnetic resonance imaging techniques for evaluation of left ventricular function
Hjärtinfarkt är en av de vanligaste anledningarna till för tidig död. Vid en hjärtinfarkt dör delar av hjärtmuskeln på grund av att den utsätts för mycket kraftig syrebrist när ett kranskärl täpps till. Även hjärtmuskelvävnad i infarktens närhet påverkas. Hjärtats vänsterkammare förser kroppen med syresatt blod. Exakt hur vänsterkammarens funktion påverkas under de första dagarna efter hjärtinfarkt, och hur vänsterkammaren återhämtar sig över tid är inte helt utrett. Trots att det finns många metoder för att utvärdera vänsterkammarens funktion så finns det behov att ytterligare utveckla reproducerbara mått. På så sätt kan förståelsen och diagnostiken av hjärtsjukdomar förbättras. Magnetisk resonanstomografi, vanligen kallad MR, används i samtliga delarbeten i denna avhandling för undersökning av patienter, friska frivilliga och försöksdjur samt i fantomexperiment. MR anses vara den mest tillförlitliga metoden när det gäller mätning av hjärtats volymer, hjärtinfarktstorlek och blodflöden i hjärtat.I delstudie 1 utvärderades en ny metod (hastighets-kodad strainmätning), som har potential för klinisk användning, för bestämning av töjning (strain) av vänsterkammarmuskeln. Metoden använder speciella hastighetskodade bilder av hjärtat tagna med magnetkamera och är utvecklad av hjärt-MR gruppen vid Lunds Universitet. När hastighetskodad strain med MR jämfördes med en oberoende, optisk metod i modellförsök påvisades god överensstämmelse. Metoden testades sedan vidare på 36 friska försökspersoner och referensvärden för strain togs fram. Metoden provades också på 10 personer efter hjärtinfarkt och man kom fram till att strain är generellt sänkt hos patienter efter hjärtinfarkt jämfört med friska försökspersoner. I delstudie 2 mättes strain och väggförtjockning av hjärtats vänsterkammarmuskel före och efter hjärtinfarkt i försöksdjur. Syftet var att undersöka hur vänsterkammarens funktion förändrades akut efter hjärtinfarkt och att undersöka om det var möjligt att skilja på områden med infarkt, områden nära och områden långt från infarkten med hjälp av strain och väggförtjockning. Resultatet blev att dessa områden uppvisade klara skillnader i statistiskt hänseende men att precisionen inte var tillräckligt hög för att kunna användas på patienter.I delstudie 3 undersöktes vänsterkammarens funktion hos 177 patienter från 2 internationella forskningsstudier en vecka efter hjärtinfarkt samt hos 20 friska frivilliga försökspersoner. Förkortning av vänsterkammaren under hjärtcykeln, strain i vänsterkammarväggen samt väggförtjockning undersöktes i olika delar av vänsterkammaren. Resultaten visade sänkt vänsterkammarfunktion avseende både förkortning, strain och väggförtjockning hos patienter efter hjärtinfarkt jämfört med friska försökspersoner. Den sänkta funktionen påvisades både i områden med infarkt och områden utan infarkt, dvs. även i delar av hjärtmuskeln som inte varit utsatta för syrebrist. Den sänkta funktionen stod i proportion till infarktstorleken. I delstudie 4 undersöktes 77 patienter från delstudie 3 som genomgått ytterligare en MR-undersökning 6 månader efter hjärtinfarkten. Studien visar att det skedde en viss förbättring av vänsterkammarfunktionen mellan undersökningstillfällena men att funktionen var fortsatt sänkt, både i områden med och utan infarkt
The 24-lead ECG display for enhanced recognition of STEMI-equivalent patterns in the 12-lead ECG.
In a patient with chest pain and suspected acute coronary syndrome, the electrocardiogram (ECG) is the only readily available diagnostic tool. It is important to maximize its usefulness to detect acute myocardial ischemia that may evolve to myocardial infarction unless the patient is treated expediently with reperfusion therapy. Since diagnostic guidelines have usually included only ST-elevation myocardial infarction (STEMI) as the entity that should be diagnosed and treated urgently, a patient with coronary occlusion represented on ECG as ST depression is likely not to be considered a candidate for receiving immediate coronary angiography and coronary intervention. ECG criteria for STEMI detection require that ST elevation meet predetermined millivolt thresholds and appear in at least two spatially contiguous ECG leads. The typical ECG reader recognizes only three contiguous pairs: aVL and I; II and aVF; aVF and III. However, viewing the "orderly sequenced" 12-lead ECG display, two more contiguous pairs become obvious in the frontal plane: +I and -aVR; -aVR and +II. The 24-lead ECG is a display of the standard 12-lead ECG as both the classical positive leads and their negative (inverted) counterparts. Leads +V1, +V2, +V3, +V4, +V5, and +V6 and their inverted counterparts are used to generate a "clock-face display" for the transverse plane. Similarly, +aVL, +I, -aVR, +II, +aVF, +III in the frontal plane and their inverted counterparts are used to generate a clock-face display for the frontal plane. Optimum results, 78% sensitivity and 93% specificity, were obtained using the following 19 ECG leads: frontal plane: +aVR, -III, +aVL, +I, -aVR, +II, +aVF, +III, -aVL; transverse plane: +V1, +V2, +V3, +V4, +V5, +V6, -V1, -V2, -V3
Use of the 24-lead "standard" electrocardiogram to identify the site of acute coronary occlusion
This review presents the added value for diagnosis of acute ischemia/infarction of considering ST elevation in the 12 inverted leads (-I, -II, -II, -aVR, etc) of the standard electrocardiogram in addition to ST elevation in 12 positive leads. A small number of studies have been published showing substantial increases in sensitivity at the "cost of' slight decreases in specificity. One recent study indicated that only 7 of the inverted leads should be considered, yielding a "19-lead electrocardiogram" encompassing the following leads (presented here in the logical secquences): -III, aVL, I, -aVR, II, aVF, III, -aVL, -I, aVR; and V1, V2, V3, V4, V5, V6, -V1, -V2, -V3. Studies have to be performed to establish the thresholds that should be applied to these leads for achievement of sensitivity/specificity
Maximal increase in sensitivity with minimal loss of specificity for diagnosis of acute coronary occlusion achieved by sequentially adding leads from the 24-lead electrocardiogram to the orderly sequenced 12-lead electrocardiogram
Objectives: This study investigates whether sequential addition of inverted, (negative) leads from the 24-lead electrocardiogram (ECG) to the orderly sequenced 12-lead ECG would identify a number of leads with which the sensitivity for diagnosis of acute transmural ischemia is significantly increased with minimal loss of specificity. Background: Acute transmural ischemia due to thrombotic coronary occlusion typically progresses to infarction. Its recognition is based on currently accepted ST-elevation myocardial infarction (STEMI) criteria with suboptimal sensitivity, which could be potentially increased by consideration of the principle that each of the 12 ECG leads can be inverted to provide an additional lead with the opposite (180 degrees) orientation, generating a 24-lead ECG. Methods: The study population included 162 patients who underwent prolonged coronary occlusion during elective percutaneoas transluminal coronary angioplasty. Balloon occlusion was performed in the left anterior descending coronary artery (51 patients), in the right coronary artery (67 patients), or in the left circumflex coronary artery (44 patients). To be classified as indicative of the epicardial injury current of acute ischemia, the ECGs had to fulfill either the criteria of a consensus document from the American College of Cardiology or the European Society of Cardiology or thresholds for the inverted leads based on a population study from Scotland. Results: The addition of -V1, -V2, -V3, -aVL, -I, aVR, and -III increased sensitivity from 61% to 78% (P <= .01) and decreased specificity from 96% to 93% (P = .06). Conclusions: Addition of 7 leads from the 24-lead ECG, thus creating a 19-lead ECG, was found optimal for attaining high sensitivity while retaining high specificity when compared with the performance of the standard 12-lead ECG. (C) 2007 Elsevier Inc. All rights reserved
Comparison of teaching the basic electrocardiographic concept of frontal plane QRS axis using the classical versus the orderly electrocardiogram limb lead displays
This study compares the effectiveness of teaching the calculation of frontal plane QRS axis with the use of the classical versus the orderly electrocardiographic limb lead display. Eighty-three students from two environments were randomized into two groups and were taught to determine frontal plane axis with one of the methods. The accuracy and time to determine the axis were tested on 10 electrocardiograms. In the United States the group using the classical display achieved 4.2 (+/-2.7) correct answers, whereas those using the orderly method achieved 6.8 (+/-3.0) (p = 0.0006). The classical group used 9.2 (+/-2.8) minutes to complete the test, whereas the orderly group needed 7.2 (+/-2.0) minutes (p = 0.015). The results achieved in Sweden were similar. The use of the orderly electrocardiographic limb lead display results in greater diagnostic accuracy in less time than the classical display when determining the frontal plane QRS axis
Regional myocardial strain at rest as assessed by velocity-encoded CMR remain unchanged in endurance trained athletes compared to normal subjects
Reducing search times and entropy in hospital emergency departments with real-time location systems
Although the consequences of hospital ED crowding have been studied extensively, the causes of crowding are still not well understood. Throughput factors in ED crowding models are difficult to study in a controlled fashion in a dynamic environment where healthcare demand changes rapidly, and physical and human resources suddenly become limited. Opportunities for automated, simultaneous, and low-cost observation of the location and movement of multiple units, patients and staff have recently arisen with the introduction of small, non-intrusive real-time location systems (RTLS). One such RTLS deployment reported here has initiated renewed consideration of quality and industrial statistics as applied to healthcare operations management. Novel metrics for essential constructs of throughput factors in ED crowding such as efficiency and effectiveness are proposed. In particular, causality is explained in terms of understanding of each construct, modeled in terms of entropy, information, and order. Experimental demonstration is given of how labor reduction and the probability of patients, personnel and equipment meeting in terms of less uncertainty can be explained. These novel metrics are expected to facilitate monitoring of how an ED reacts to different levels of crowding, provide insight into crowding dynamics, help evaluate interventions to decrease crowding, and ultimately improve care