ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Our purpose was to describe a technique of atrioventricular (AV) node modification for patients with drug refractory AV nodal reentrant tachycardia (AVNRT). Nine patients (mean age, 45±20; range, 14–82) with recurrent drug refractory AVNRT (n= 8) or sudden cardiac death thought to be precipitated by AVNRT (n= 1) underwent a percutaneous catheter procedure to modify AV nodal function. The area between the electrode recording the maximal His-bundle electrogram and the ostium of the coronary sinus was divided into three zones. Perinodal direct current shocks of 100–300 J were delivered to one (n= 2), two (n= 3), or three (n= 4) zones without complications. The procedure endpoints were modification of AV conduction (either first degree AV block or complete retrograde ventriculo-atrial [VA] block) and failure to induce AVNRT before or after isoproterenol and/or atropine administration. Six of nine patients (67%) have had no inducible or spontaneous AVNRT over a mean follow-up of 12.3 ±4.1 months (range, 4.5–17). One of the six underwent repeat, successful modification, because AVNRT was inducible at restudy 2 days after the initial procedure. AVNRT recurred in three patients (33%), one early (3 days) and two late (3–4 months). Two of these patients underwent complete ablation of the AV junction and permanent pacemaker placement, whereas one is controlled with drug therapy. Therefore, AV nodal modification resulted in tachycardia control without antiarrhythmic drugs in six of nine (67%) and obviated the need for complete AV junctional ablation in seven of nine patients (78%). Elimination of AVNRT appears to result from either block in the retrograde fast pathway or modification of the antegrade slow pathway, such that AVNRT cannot be sustained. Additional findings suggest that an atrio-Hisian accessory connection may not be involved in AVNRT in some of these patients. Percutaneous catheter AV nodal modification appears to be a promising technique for treatment of refractory AVNRT and may obviate need for complete AVjunctional ablation in a substantial number of patients with drug/pacemaker refractory AVNRT.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

We studied the central hemodynamic, leg blood flow, and metabolic responses to maximal upright bicycle exercise in 30 patients with chronic heart failure attributable to severe left ventricular dysfunction (ejection fraction, 24±8%) and in 12 normal subjects. At peak exercise, patients demonstrated reduced oxygen consumption (15.1±4.8 vs. 32.1Plusmn;9.9 ml/kg/min,p<0.001), cardiac output (8.7±3.2 vs. 18.6± 4.4 1/min,p< 0.001), and mean systemic arterial blood pressure (116±15 vs. 135±13 mm Hg,p< 0.01) compared with normal subjects. Leg blood flow was decreased in patients versus normal subjects at rest and matched submaximal work rates and maximal exercise (2.1±1.9 vs. 6.4±1.4 1/min, allp< 0.01). Mean systemic arterial blood pressure was no different in the two groups at rest or at matched submaximal work rates, whereas leg vascular resistance was higher in patients compared with normal subjects at rest, submaximal, and maximal exercise (allp< 0.01). Although nonleg blood flow was decreased at rest in patients, it did not decrease significantly during exercise in either group. Peak exercise leg blood flow was related to peak exercise cardiac output in patients (r= 0.66,p< 0.01) and normal subjects (r= 0.67,p< 0.01). In patients, leg vascular resistance was not related to mean arterial blood pressure, pulmonary capillary wedge pressure, arterial catecholamines, arterial lactate, or femoral venous pH at rest or during exercise. Compared with normal subjects during submaximal exercise, patients demonstrated increased leg oxygen extraction and lactate production accompanied by decreased leg oxygen consumption. Thus, in patients with chronic heart failure compared with normal subjects, skeletal muscle perfusion is decreased at rest and during submaximal and maximal exercise, and local vascular resistance is increased. Our data indicate that nonleg blood flow and arterial blood pressure were preferentially maintained during exercise at the expense of leg hypoperfusion in our patients. This was associated with decreased leg oxygen utilization and increased leg oxygen extraction when compared to normal subjects, providing further evidence that reduced perfusion of skeletal muscle is important in causing early anaerobic skeletal muscle metabolism during exercise in subjects with this disorder. Although these results do not define the mechanisms responsible for increased leg vascular resistance during exercise in subjects with chronic heart failure, our finding that arterial blood pressure in patients was closely regulated suggests a role for reflex-mediated peripheral vasoconstriction in linking the cardiac output and skeletal muscle blood flow responses to exercise in subjects with this disorder.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Percutaneous transvenous mitral commissurotomy was performed in 106 consecutive patients. Significant symptomatic improvement was achieved in 97 patients (92%). Mean left atrial pressure decreased (from 18±8 to 11±8 mm Hg,p< 0.00001), mean mitral diastolic pressure gradient decreased (from 12±7 to 7±6 mm Hg,p<0.00001), and mitral valve area increased (from 1.40± 0.40 to 2.00 ±0.50 cm2,p< 0.00001). Based on echocardiographic characteristics of the mitral apparatus, patients were grouped retrospectively in three categories: pliable (group 1,n=37), semipliable (group 2,n=59), and rigid (group 3,n= 10). Clinical success was achieved in 36 patients of group 1 (97%) and in 55 patients of group 2 (93%). Only six patients in group 3 (60%) improved symptomatically (p<0.001 vs. group 1,p< 0.001 vs. group 2). The severity of mitral regurgitation increased in five patients of group 1 (14%), in 12 of group 2 (20%), and in three of group 3 (33%). Six patients had recurrent symptoms at 9 months after commissurotomy. Recurrence of symptoms was significantly more frequent in group 3 compared with the other two groups (group 1, 3%; group 2, 4%; and group 3, 50%;p< 0.0001 vs. groups 1 and 2). Multiple regression analysis identified the previously mentioned echocardiographic characteristics of the mitral apparatus as the significant predictor for clinical outcome. Thus, percutaneous transvenous mitral commissurotomy can be considered a safe and effective treatment for patients with pliable valves. Patients with semipliable or with rigid valves should be selected for operation very carefully.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The purpose of this study was to define specific types of resetting responses to programmed electrical stimulation during human ventricular tachycardia and to use computer simulations of reentry circuits to assess the possible mechanisms and pacing site location relative to the reentry circuit for each type of response. The effects of scanning single stimuli at 35 left ventricular endocardial sites during sustained monomorphic ventricular tachycardia in 12 patients were studied. In considering alterations in QRS configuration and the delay between the stimulus and the advanced QRS, we identified three types of resetting responses to scanning stimuli consistent with stimulation at sites in or near the reentry circuit at 12 abnormal endocardial sites in eight patients. Type 1: all capturing stimuli were followed after a delay by early QRS complexes that had the same configuration as the tachycardia complexes. Type 2: late stimuli reset tachycardia as in type 1 but early stimuli reset the tachycardia after altering the QRS configuration. Type 3: late stimuli reset tachycardia as in type 1, but early stimuli advanced tachycardia with a short stimulus to QRS delay without altering the QRS configuration. In the simulations, premature depolarization of sites in the circuit produced orthodromic and antidromic wavefronts. The orthodromic wavefront propagated through the circuit and exited the circuit at the same site as did the previous tachycardia wavefronts and advanced the tachycardia without altering the configuration of the advanced QRS. The antidromic wavefront of relatively late stimuli was confined within or near the circuit by collision with the orthodromic wavefront of the preceding tachycardia beat and failed to alter ventricular activation distant from the circuit. Therefore, the QRS configuration after the stimulus was unchanged. A type 1 response occurred when all capturing stimuli produced this effect. However, with increasing stimulus prematurity, the antidromic wavefront propagated farther before colliding with an orthodromic wavefront, and under some conditions, it exited the circuit from a site other than the original circuit “exit,” and altered the ventricular activation sequence distant from the circuit and, therefore, the QRS configuration, producing a type 2 pattern. The type 3 pattern occurred when the antidromic wavefront of early premature beats captured the original circuit exit. The effect of a stimulus was dependent on the stimulus prematurity, the relative conduction times from the stimulation site to the potential sites of “exit” from the circuit, and the timing of the excitable gap at the stimulation site. In the figure-eight reentry circuit simulations, the type 1 response tended to occur during stimulation within, the type 2 response near the entrance to, and the type 3 response outside but near the exit from the slowly conducting central common pathway. Type 2 responses could also occur with stimulation at a site that was close to but not within the circuit. The recognition of specific responses characteristic of programmed stimulation at reentry circuit sites is feasible in humans and may improve ventricular reentry circuit localization by catheter techniques. However, at some circuit sites, stimulation may alter ventricular activation distant from the circuit and falsely suggest that the site is not within the circuit. The potential variability of electrophysiologic and spatial factors that influence the response to programmed stimulation may limit precise determination of the stimulation site location relative to critical areas in the circuit.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Seventy-four consecutive patients with angina undergoing single-lesion percutaneous transluminal coronary angioplasty were evaluated with high-dose (up to 0.84 mg/kg during 10 minutes) dipyridamole echocardiography test (DET) before angioplasty and when possible, afterward. Angioplasty was clinically or angiographically successful in 63 patients and unsuccessful in 11. Before the procedure, 69 patients had a positive DET. Of these 69 patients, six with clinically unsuccessful angioplasty had a dipyridamole time (i.e., the time from the onset of dipyridamole infusion to development of asynergy) lower than the 63 patients with clinically successful angioplasty (4.2±2.9 vs. 7.0±2.9 minutes, mean±SD,p< 0.01). In the five patients with angiographically unsuccessful angioplasty (residual stenosis diameter, >50%), coronary stenosis decreased from 89±10 to 69±22 (p= NS); DET was positive in all five before and in four of the five after the procedure (100% vs. 80%o,p= NS). In the 63 patients with angiographically successful angioplasty, coronary stenosis diameter was reduced from 85±9% to 30±10% (p< 0.01). DET was positive in 58 patients before and in only 16 after the procedure (92% vs. 25%,p< 0.01). In the 16 patients with positive DET, before and after angioplasty, dipyridamole time increased from 5.6±2.2 before to 7.3±2.4 minutes immediately after the procedure (p< 0.05). After an average follow-up time of 10.8±5.9 months, angina recurred in eight of 47 patients with negative DET after angioplasty and in 11 of 16 patients with positive DET (17% vs. 69%,p< 0.01). When angina symptoms recurred, a third DET was performed 1–3 days before repeat coronary angiography in 11 patients (3.6±2.7 months after the angioplasty). DET was positive in 10 of these patients, and all had coronary restenosis at angiography. DET was negative in the remaining patient, and this patient had no restenosis at angiography. These findings show that 1) before angioplasty, DET positivity with a very low dipyridamole time identifies a subset of patients at relatively higher risk of an unsuccessful procedure, 2) there is an excellent general correlation between the functional improvement assessed by DET and anatomic results of angioplasty, 3) DET positivity soon after successful angioplasty identifies a group at high risk for later recurrence of symptoms, and 4) when symptoms recur after angioplasty, DET positivity reliably identifies coronary restenosis.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Hypertrophy of the noninfarcted left ventricle as a chronic response to myocardial infarction has been demonstrated in animals and at autopsy in humans. However, the functional significance of postmyocardial infarction hypertrophy is a subject of dispute. The purpose of this study was to determine the time course of development of postmyocardial infarction hypertrophy of the noninfarcted myocardium in humans and to assess its functional significance. Subcostal view, two-dimensional echocardiograms were recorded at rest and during peak exercise, 6 and 40 weeks postmyocardial infarction in 45 patients (16 anterior, 20 inferior, nine non-Q wave infarcts), for measurement of left ventricular mass and ejection fraction. The left ventricular mass index increased from 94±30 to 118±27 g/m2(p< 0.01) during the time of the two studies. There was a significant correlation between the change in left ventricular mass index and improved resting ejection fraction (r= 0.48,p< 0.001) and exercise ejection fraction (r= 0.48,p<0.001) at the follow-up study. Of the 32 patients who increased their left ventricular mass index >7%, 18 improved their rest ejection fraction >0.05 units and 17 improved their exercise ejection fraction >0.05 units. Conversely, of the 13 patients who failed to increase their left ventricular mass index, only three improved their rest ejection fraction and one improved the exercise ejection fraction (Fisher's exact test,p< 0.05). We reached three conclusions. First, in humans, significant hypertrophy of the noninfarcted myocardium can be detected by two-dimensional echocardiography, 9 months postmyocardial infarction. Second, patients who demonstrate hypertrophy of the noninfarcted myocardium are more likely to demonstrate improved rest and exercise ejection fraction than those who do not. Third, postmyocardial infarction left ventricular hypertrophy may, therefore, represent a beneficial chronic adaptation to the loss of myocardium after myocardial infarction.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Chronic right ventricular pressure overload is associated with left ventricular diastolic dysfunction. Whether or not an abrupt reduction in pulmonary artery pressure in patients with chronic pulmonary hypertension results in early improvement of left ventricular diastolic function is unknown. To assess this, the Doppler indexes of left ventricular diastolic function and echocardiographic measures of left ventricular volume were analyzed in 22 patients (age, 41±14 years, mean±SD) before and within 1 week after pulmonary thromboendarterectomy for chronic thromboembolic pulmonary hypertension. Mean duration of cardiopulmonary symptoms was 37 months (range, 4 months to 9 years). After operation, mean pulmonary artery pressure and pulmonary vascular resistance decreased (50±13 to 29±9 mm Hg and 904±654 to 283±243 dynes sec/cm5, respectively, bothp< 0.001), pulmonary artery wedge pressure was unchanged (11±5 to 12±5 mm Hg), and cardiac index increased (2.0±0.5 to 2.8±0.7 1/min/m2p< 0.001). Left ventricular end-diastolic volume and stroke volume increased significantly (58.5±18.0 to 76.6±25.0 ml and 30.3±12.3 to 41.8±12.5 ml, respectively, bothp< 0.001) after surgery. Doppler measures of left ventricular diastolic function including peak early velocity of mitral inflow, deceleration of early filling, and early to late peak flow velocity ratio increased with surgery (48±20 to 79±24 cm/sec,p< 0.001, 2.6±1.4 to 4.2±1.8 m/sec2,p< 0.002, and 1.04±0.42 to 1.67±0.60,p< 0.001, respectively), whereas peak atrial velocity did not change significantly (48±10 to 49±9 cm/sec). Furthermore, the indexes of left ventricular relaxation correlated with the end-systolic position of the interventricular septum as assessed by two-dimensional echocardiography (allp< 0.001). Thus, Doppler-derived indexes of left ventricular diastolic function improve markedly early after pulmonary thromboendarterectomy in patients with pulmonary hypertension despite long-standing symptoms. The changes in these indexes of left ventricular diastolic function, which correlate with changes in the position of the interventricular septum and occur in the setting of increases in left ventricular volume, suggest that abnormal left ventricular diastolic function seen in right ventricular pressure overload is a consequence of the right-left ventricular interaction and is mediated in large part through the interventricular septum.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Balloon aortic valvotomy (BAV) is an alternative to surgical valvotomy in infants and children. We compared BAV in 16 consecutive neonates (1985–1988) to surgical valvotomy in a prior group of 16 consecutive neonates (1978–1984). Both groups were comparable in terms of age, weight, hemodynamic data, left ventricular size, and associated lesions. There were six early and one late deaths after surgery. Five out of six neonates requiring a second operation died. Left ventricular size (measured in 13 neonates) had some influence on survival after surgery: three of three with small or hypoplastic left ventricles and three of 10 with normal-sized left ventricles died. After BAV, there were three early deaths, two patients who underwent stage I palliation of hypoplastic left heart syndrome, and two late deaths. As with surgical valvotomy, left ventricular size seemed to influence survival after BAV: five of six with small or hypoplastic left ventricles died or underwent stage I palliation for hypoplastic left heart syndrome and two of nine with normal-sized left ventricles died. At follow-up (26±17 months) in six patients in the surgical group, the peak systolic ejection gradient (PSEG) was 52.2±23 mm Hg and left ventricular end-diastolic pressure (LVEDP) 18.2±5.2 mm Hg. Aortic regurgitation was mild in five and moderate in the sixth patient. At follow-up (17.6±7.8 months) in nine patients in the balloon dilation group, the PSEG was 45.6±11 mm Hg in five patients at catheterization and 43.8±22.9 mm Hg in four patients by echocardiography-Doppler. Aortic regurgitation was mild in three and absent in the other six patients. BAV may be an effective alternative to surgical valvotomy in unselected neonates with critical valvar aortic stenosis.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The long-term clinical course was studied in 646 patients, who underwent isolated operative repair of coarctation of the aorta at the Mayo Clinic from 1946 to 1981. There were 17 perioperative deaths, and 58 patients were lost to follow-up. Of the 571 patients with long-term follow-up, 11% required subsequent cardiovascular surgery, and 25% developed hypertension. There were 87 late deaths. The mean age at death was 38 years (range, 0–67 years). Estimated survival analysis revealed 91% of patients alive at 10, 84% at 20, and 72% at 30 years after operative repair. The most common cause of late death was coronary artery disease in 32 patients, followed by sudden death, heart failure, cerebrovascular accidents, and ruptured aortic aneurysm. Age, sex, and postoperative systolic blood pressure were found to be independently predictive of survival. For patients less than 14 years of age at the time of initial coarctectomy, survival to 20 years was 91%, and for patients 14 years or older at the time of operation, survival was 79%. The best survivorship was observed in patients operated on at 9 years of age or less. The higher the postoperative systolic pressure, the higher the probability of death. This study has the largest population undergoing repair of coarctation of the aorta with a median follow-up of as long as 20 years. Four main points emerged. 1) Age at the time of initial repair is the most important predictor of long-term survival. Surgery should be offered to patients after age 1 year or sooner if hypertension is severe. 2) Coronary artery disease is the most common cause of late death. 3) Age at the time of initial repair is the most important predictor of hypertension. 4) Associated cardiovascular anomalies requiring subsequent surgery are common. Therefore, all patients need continuous long-term monitoring after repair of coarctation of the aorta.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID