Predictability of aortic dissection as a function of aortic diameter

The role of aortic diameter on the occurrence of type A dissectionwas investigated in 73 patients with dilated ascending aortaat the lime of pre-operative evaluation. Using transthoracicechocardiography for diagnosis and measurements, 54 patientswere identified with type A dissection (group 1) and 19 withoutdissection (group 2). The true mean aortic diameters were identical(6·0±1·3 cm in group 1 and 6·4±1·4cm in group 2; mean±SD; ns) as were the indexed aorticdiameters (ratio of diameter/body surface area; 3·2±0·8cm . m^–12 and 3·4±0·7cm m^–2respectively; ns). However, the individual diameters showeda pronounced scatter in both groups (range from 3·6±11·0cm). Of the 73 patients, 66 had surgery (47/54 with and 19/19without dissection) and seven patients were treated medically.Emergency surgery was performed in 45/66 patients (all withacute type A dissection) andelective repair in 21/66 (19 withoutand two with chronic type A dissection). In-hospital mortalitywas 18% in the emergency group, 5% in the elective group and57% in the medical group. It is concluded that patients with dilated ascending aorta havea substantial incidence of acute dissection. Their clinicalcourse is unpredictable; acute dissection occurs in some, andin others the ascending aorta continues to enlarge without dissection.Because patients with dissection often arrive too late for electiverepair andhave to be operated on as emergencies with a higheroperative risk, we recommend elective surgery before the diameterof the ascending aorta has reached 6 cm.     

Indications for Pericardial Glutaraldehyde-Preserved Xenograft in Repair of Congenital Heart Disease

A glutaraldehyde-preserved equine pericardial xenograft was implanted in 370 patients between 1981 and 1987; pericardial sac closure in 320 (mainly over Dacron implants), atrial repairs in 19, arterial reconstructions in 22 (right outflow tract in 19, Konno's procedure in three), control of bleeding after surgery for thoracic aneurysms in seven, control of plasma leaking PTFE graft in one, and repair of diaphragmal agenesia in one. Overall infection rate was 3/370 (0.8%). Epicardial adhesions (12) at reoperation for orthotopical implants were graded 1.3 +/- 0.9 on a scale of 6 (0 = no adhesions, 5 = calcified or ossified adhesions) after 4 +/- 2 months. Shrinkage of xenograft occurred in 3/19 (16%) atrial repairs and lesser degree aneurysmal dilatation appeared in 1/19 (5%) reconstructions of the right outflow tract. No complications occurred in the implants without direct exposure to the blood stream. We recommend pericardial xenograft for Konno's procedure and control of bleeding. It should not be used routinely in the low pressure side.     

Activity-Sensing Rate Responsive Versus Conventional Fixed-Rate Pacing: A Comparision of Rate Behavior and Patient Well-Being During Routine Daily Exercise

Rate responsive single chamber pacing (WIR) may be the pacemaker of choice in pafients who are not suitable candidates for a dual chamber system. Several studies, most of them performed in an exercise laboratory, have shown a significantly higher exercise capacity demonstrating an improvement in cardiac output and anaerobic threshold compared to conventional fixed rate pacing (VVT). Expressing our idea that stress testing in an “artificial environment” on a bicycle or motor driven treadmill has its limitations and may be difficult to extend into patient's daily life, we designed an outdoor study imitating patient's daily activity. Twenty-one patients with an activity-sensing rate responsive pacemaker performed in a double blind fashion in VVI and VVIR mode the following test circuit: walking 170 meters on flat ground, 210 meters incline, climbing a flight of stairs, and the same circuit in reverse order, and therefore “downhill”. Heart rate behavior was recorded by Holter monitoring and patients subjective feelings of well-being, i.e. fatigue and dyspnea were also evaluated, VVIR pacing responded promptly to exercise, i.e., walking on a flat ground, but no further significant increase in pacing rate was observed in relationship to the strength of physical activity while walking inclined or climbing stairs. While patients became exhausted, a nonphysiological decrease in heart rate sometimes occurred. Despite these limitations 6 of 12 patients who had a paced-only rhythm while exercising in both VVI and VVIR mode reported feeling significantly belter in the VVIR mode, expressing less dyspnea and fatigue. In contrast, two of nine patients having only intermittently paced rhythm preferred the VVIR mode. Patients with lower ejection fraction (EF) were more likely to show subjectively a benefit while exercising in VVIR mode, compared to those with less reduced or normal EF. Despite the technical limitations of using a piezo crystal for rate adaptation, WIR pacing is an important option in paced-only patients, but it seems less beneficial in patients with only intermittent paced rhythm.     

Autonomic Nervous System-Controlled Cardiac Pacing: A Comparison Between Intracardiac Impedance Signal and Muscle Sympathetic Nerve Activity

BINGGELI, C., et al. : Autonomic Nervous System‐Controlled Cardiac Pacing: A Comparison Between Intracardiac Impedance Signal and and Muscle Sympathetic Nerve Activity. A recently introduced rate responsive cardiac pacing system is based on information derived from the intracardiac impedance signal containing information on the inotropic state of the ventricle. This study compared the inotropic state index (ISI) with muscle sympathetic activity (MSA), both being modulated by the autonomic nervous system. Nine patients (66 ± 3 years, mean ± SEM ) with Inos2DR pacemakers were included. Each patient was studied at rest and during cold pressor test (CPT). Microneurography of the peroneal nerve was performed to measure MSA continuously, which was digitally stored along with continuous surface ECG and blood pressure. The intracardiac impedance signal was transmitted by the pacemaker and stored simultaneously. Linear correlation between ISI and MSA was calculated for the period of the CPT. During CPT, mean systolic blood pressure increased from 122 ± 4 to 149 ± 6 mmHg (P < 0.0001), diastolic blood pressure increased from 74 ± 8 to 86 ± 4 mmHg (P = 0.02 ), and intrinsic heart rate increased from 69 ± 7 to 75 ± 7 beats/mill (P = 0.019 ). ISI increased by 21 ± 7% (P = 0.018 ), MSA by 26 ± 6% (P = 0.004 ). ISI and MSA were positively correlated during the CPT in eight of nine patients (R2 = 0.86–0.99, P < 0.0001 ). Negative correlation was found in one patient (R2 = 0.94 ). This study demonstrates parallel increases of the ISI and MSA during CPT. ISI and MSA showed a close linear relationship during provoked changes of sympathetic activity. These results provide further evidence that the sympathetic nervous system is responsible for the observed ISI changes.     

Echocardiographic findings late after myectomy in hypertrophic obstructive cardiomyopathy

Postoperative echocardiograms of 50 patients undergoing myectomyfor hypertrophic obstructive cardiomyopathy between 1965 and1982 have been evaluated. In 21 patients a comparison with preoperativeechocardiograms showed that postoperatively there was a significantreduction of septal and free wall thickness, an increase ofleft ventricular end-diastolic as well as outflow tract dimensionsand a reduction or disappearance of systolic anterior motionof the mitral leaflet. Postoperative examination at intervals> 3 years revealed a significant increase of left ventricularand left atrial cavity size with unchanged contractile parametersand little reduction of left ventricular hypertrophy. In 4of12 patients evaluated > 8 years after myectomy, left ventriculardilatation was observed and 3 of these 4 patients developedcongestive heart failure. Development of leftventricular dilatationwas independent of whether a transventricular and/or transaorticapproach was used for myectomy. These data indicate that thelate course after myectomy in hypertrophic obstructive cardiomyopathymay be complicated by dilatation of the left ventricular cavity.     

Platelet inhibitors versus anticoagulants for prevention of aorto-coronary bypass graft occlusion

The effects of the antiaggregant substance ticlopidine and ofthe anticoagulant acenocoumarol on patency rates of aorto-coronarybypass grafts were compared in a prospective randomized trial.Ticlopidine, 250 mg b.i.d. was administered orally from thefirst postoperative day till angiography, while anticoagulationwith acenocoumarol was initiated on the second to third postoperativeday. Side-effects of ticlopidine were rare and patient managementwith the standard dosage of this drug was easier than oral anticoagulation.From an initial group of 166 randomized patients 149 completedthe trial by coronary angiography three months postoperatively.The 78 patients in the ticlopidine group showed a complianceof 85%. The average prothrombin time in the 71 patients receivingacenocoumarol was 26.9%. Detailed statistical analysis of thetwo study groups revealed no reason to doubt the correctnessof randomization. Coronary angiography showed an average patency rate per patientof 84% with ticlopidine and of 82% with acenocoumarol. Thisand various other measures of graft occlusion did not revealany substantial difference in graft patency of patients receivingticlopidine or acenocoumarol. It is concluded that ticlopidinemay well be used instead of anticoagulants forprevention ofpostoperative occlusion of aorto-coronary bypass grafts     

Left ventricular relaxation at rest and during handgrip in aortic valve disease before and after valve replacement

In 14 patients (pts) with aortic valve disease (A VD) left ventricular(LV) relaxation was assessed by the time constant (T) of LVpressure (tipmanometer) fall before and 19 months after successfulaortic valve replacement (A VR). 12 control pts (CO) were studiedby the same technique. Preoperative LV ejection fraction inAVD (64%) and in CO (69%) did not differ. In AVD T was increased(60 ms) as compared to the CO (38 ms, P< 0.05). During handgrip(HG) there was a similar increase of LV peak systolic pressure(LVSP), heart rate and peak measured contractile element velocityof shortening in A VD and in the CO. L V end-diastolic pressurevaried minimally in both groups. T decreased during handgripin CO (38 to 33 ms, P<0.01) and remained unchanged in A VD.Following AVR T at rest decreased insignificantly to 52 ms,but remained increased (P<0.025) as compared with CO. Duringpostoperative HG however, a decrease to 47ms (P<0.05) wasnoted. Postoperative angiographic LV muscle mass (105 g/m²)and LVSP at rest (137 mmHg) remained elevated (P<0.02) ascompared to CO (72 g/m²; 119 mmHg). It is concluded that (1)in A VD with normal ejection performance L V relaxation at restis prolonged and the reaction of relaxation to HG is abnormaldespite preserved contractile response, (2) following A VR theresponse of LV relaxation to HG becomes normal and (3) elevatedpostoperative T at rest appears to be related to residual hypertrophyand probably also to the still increased LVSP rather than tointrinsic disturbances of myocardial relaxation.