RESUMO
The role of cycle length and cycle length alternans in the induction of tachycardia-related QRS electrical alternans was investigated using an atrial pacing protocol in 16 patients. Pacing was performed at a cycle length less than 400 ms in 5 patients, greater than 400 ms in 5 and at both in 6 with 0, 6, 10, 20, 40 and 60 ms of atrial cycle length alternans. A 12-lead electrocardiogram and high right atrial, His bundle and right ventricular apical electrograms were simultaneously recorded after 30 to 60 seconds of pacing. Alternans was produced in 88% of patients. Alternans was 3 times more frequent at short (less than 400 ms) than long paced cycle lengths (greater than 400 ms) (66% vs 22%, p less than 0.0001). Alternans increased with increasing cycle length alternans and occurred with very little (less than or equal to 10 ms) atrioventricular nodal, His-Purkinje and ventricular cycle length alternans when paced cycle length was short. Alternans was more frequent in the precordial than the limb leads (45% vs 17%, p less than 0.001) and was most frequent in V3 and V2 (sensitivity 69% and 65%) and least frequent in leads I and aVL (sensitivity 4% and 10%). More leads per electrocardiogram showed alternans at short compared with long paced cycle lengths and the number of leads per electrocardiogram increased with increasing cycle length alternans. Occurrence of alternans was highly related to QRS amplitude by Spearman rank correlation (p less than 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Estimulação Cardíaca Artificial , Eletrocardiografia , Sistema de Condução Cardíaco/fisiopatologia , Taquicardia Supraventricular/fisiopatologia , Eletrofisiologia , Feminino , Átrios do Coração , Humanos , Masculino , Pessoa de Meia-Idade , Taquicardia Supraventricular/diagnósticoAssuntos
Angiocardiografia , Pressão Sanguínea , Doença das Coronárias/fisiopatologia , Contração Miocárdica , Polietilenos , Sístole , Adulto , Idoso , Doença das Coronárias/diagnóstico por imagem , Diástole , Feminino , Ventrículos do Coração/fisiopatologia , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
Two patients with Wolff-Parkinson-White syndrome and surgically mapped anterior left free wall atrioventricular bypass tracts had orthodromic atrioventricular reentry tachycardia conducted with complete left bundle branch block (CLBBB), complete right bundle block (CRBBB), left anterior fascicular block (LAFB), and a narrow QRS. Ventriculoatrial conduction increased by 35 and 85 ms with CLBBB compatible with the left free wall location of the bypass tracts. In one patient, resolution of CLBBB occurred in two stages. Initially, left posterior fascicular block (LPFB) resolved, decreasing VA conduction by 20 ms. With resolution of the remaining LAFB, there was a further 15 ms decrease in VA conduction. In the other patient, the isolated occurrence of LAFB increased ventriculoatrial conduction by 30 ms. These changes confirmed the location of the bypass tracts in the anterior portion of the left ventricular free wall. Changes in VA conduction with fascicular block can help localize the ventricular insertion of atrioventricular bypass tracts.
Assuntos
Nó Atrioventricular/fisiopatologia , Bloqueio de Ramo/fisiopatologia , Sistema de Condução Cardíaco/fisiopatologia , Taquicardia por Reentrada no Nó Atrioventricular/fisiopatologia , Taquicardia Supraventricular/fisiopatologia , Síndrome de Wolff-Parkinson-White/fisiopatologia , Adulto , Humanos , MasculinoRESUMO
This study was done to determine the accuracy and reliability of cardiac output measurements by the injection of indocyanine green into the left ventricle, with simultaneous sampling from a systemic artery. In 40 patients (18 men, 22 women, aged 34 to 74 years), cardiac output was measured in close temporal proximity by (a) standard indicator dilution (right atrium-to-pulmonary artery thermodilution in 11, pulmonary artery-to-systemic artery indocyanine green in 29) and (b) left ventricle-to-systemic artery indocyanine green. There was excellent agreement between the two techniques (r = 0.98, SEE = 0.12 liters/minute). In 28 of the patients, cardiac output also was measured by ascending aorta-to-systemic artery indocyanine green. In these individuals, this technique yielded results that were disparate from those obtained by standard indicator dilution (difference between standard indicator dilution and left ventricle-to-systemic artery indocyanine green = 0.18 +/- 0.13 [mean +/- SD] liters/minute; difference between standard indicator dilution and ascending aorta-to-systemic artery indocyanine green = 0.72 +/- 0.55 liters/minute; p less than 0.001), and in 22 of the 28, the ascending aorta-to-systemic artery indocyanine green cardiac outputs were greater than those obtained by standard indicator dilution. Thus, cardiac output can be measured accurately by injecting indocyanine green into the left ventricle, with simultaneous sampling from a systemic artery, but it cannot be quantified reliably by introducing indicator into the ascending aorta. The left ventricle-to-systemic artery indocyanine green technique can be used in patients undergoing only left heart catheterization.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Débito Cardíaco , Técnicas de Diluição do Indicador , Adulto , Idoso , Aorta , Cateterismo Cardíaco , Feminino , Ventrículos do Coração , Humanos , Verde de Indocianina/administração & dosagem , Injeções , Masculino , Métodos , Pessoa de Meia-IdadeRESUMO
In patients with atherosclerotic coronary artery disease, cigarette smoking increases myocardial oxygen demand but may cause an inappropriate decrease in coronary blood flow and myocardial oxygen supply. This study was performed to explore the mechanism of smoking-induced coronary vasoconstriction and, specifically, to determine if smoking causes an alpha-adrenergically mediated increase in coronary artery tone. In 36 chronic smokers with coronary artery disease (27 men and nine women, 50 +/- 9 [mean +/- SD] years old), heart rate-systolic arterial pressure double product and coronary sinus blood flow (by thermodilution) were measured before and during smoking both before and after (1) normal saline (n = 5, control subjects), (2) an alpha-adrenergic-blocking agent, phentolamine, 5 mg (n = 15), (3) a beta-adrenergic-blocking agent, propranolol, 0.1 mg/kg (n = 12), or (4) sodium nitroprusside, 0.4 to 0.8 micrograms/kg/min, given in a dose sufficient to diminish systolic arterial pressure by 15% (n = 4). During the initial smoking period, rate-pressure product increased and coronary sinus blood flow was unchanged by smoking in all groups. After 30 to 75 min, saline, phentolamine, propranolol, or sodium nitroprusside was given, and measurements were repeated. In the control subjects, rate-pressure product and coronary sinus blood flow responded in a similar manner to that observed previously. In those receiving phentolamine, rate-pressure product was unchanged, but coronary sinus blood flow rose substantially with smoking (percent change +2 +/- 15% during the first smoking period [before phentolamine] and +32 +/- 17% during the second smoking period [after phentolamine]; p less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Arteriosclerose/fisiopatologia , Doença das Coronárias/fisiopatologia , Fumar , Vasoconstrição , Adulto , Idoso , Vasos Coronários/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Propranolol/administração & dosagem , Fluxo Sanguíneo RegionalRESUMO
BACKGROUND: Implantable cardioverter-defibrillators (ICDs) with intravenous electrode systems and downsized generators can be implanted by use of operative techniques similar to those employed for the insertion of permanent pacemakers. However, the safety, efficacy, and long-term follow-up of simplified implantation procedures remain to be evaluated. This report is a prospective long-term evaluation of nonselected patients receiving ICDs in the prepectoral subfascial position under conscious sedation. METHODS AND RESULTS: Clinical characteristics of the 231 consecutive patients included a mean age of 63 years, a male-to-female ratio of 6.4, a left ventricular ejection fraction of 0.34, a mild-to-moderate heart failure in 91%, coronary artery disease in 84%, and a history of aborted sudden cardiac death or refractory ventricular tachyarrhythmias. Insertion of transvenous leads and prepectoral subfascial ICD implantation were performed in electrophysiology laboratories under local anesthesia and conscious sedation with intravenous midazolam and propofol. Successful implantation in all patients (operation time, 80 +/- 32 minutes, mean +/- SD) irrespective of body size and skin thickness was free of major complications, including need for emergency intubation. After surgery, 1 pocket hematoma, 1 seroma, and 1 pneumothorax required treatment. There was no operative or first-month mortality. During long-term follow-up averaging 453 +/- 296 days, six leads required repositioning, but pocket erosions or infections did not occur. First-year total survival was 97%. CONCLUSIONS: Implantation under conscious sedation of ICDs in the prepectoral subfascial position is a safe and effective procedure with low operative and postoperative morbidity and favorable long-term outcome.