Effects of alpha adrenergic blockade upon coronary hemodynamics.

The effect of alpha adrenergic block-ade on coronary blood flow regulation at rest was studied in 11 normally innervated patients and 8 cardiac allograft recipients by measuring arterial pressure and coronary sinus blood flow by thermodilution before and after alpha adrenergic blockade with phentolamine. Coronary vascular resistance was calculated by using coronary sinus blood flow and mean arterial pressure, and metabolic demand was estimated by the product of systolic arterial pressure and heart rate. In addition, the coronary sinus blood flow response to tachycardia was examined in 9 innervated patients and 12 denervated patients, with measurements repeated after phentolamine in 8 of the 9 innvervated patients and 6 of the 12 denervated patients. There was a 7.3+/-4.4% increase in coronary sinus blood flow in the innervated patients in response to alpha blockade, whereas the transplanted patients had an 8.2+/-1.8% fall in coronary sinus blood flow, despite equivalent changes in rate pressure product. The innervated patients also demonstrated a significantly greater increase in coronary sinus blood flow than did the transplanted patients during the first 5 s of an abrupt increase in heart rate (26+/-4 vs. 8+/-2.5 ml/min, P <0.001). This early response was blunted after alpha adrenergic blockade. We conclude that there is basal alpha adrenergic tone present on the coronary vasculature in man that is withdrawn by a sudden increase in heart rate.

Role of tachycardia as an inotropic stimulus in man.

We examined the inotropic effect of tachycardia in nine postsurgical aortocoronary bypass graft patients (with intact cardiac innervation) and nine cardiac allograft recipients (with denervated hearts). The changes in stroke volume (SV) and velocity of circumferential fiber shortening (VCF) which accompany sudden increases and decreases in atrial pacing frequency were determined by computer-aided fluoroscopic analysis of the motion of surgically implanted midwall myocardial markers. Because the first beat after a change in rate retains the frequency characteristics of the preceding rate, we compared the first posttachycardia beat with control beats and late tachycardia beats with the first tachycardia beat; afterload and preload for each pair of beats were similar. For an increase in heart rate of 50 beats/min, SV and VCF rose 79 and 64% from the first tachycardia beat to late tachycardia beats, and SV and VCF rose 8 and 35% from control beats to the first posttachycardia beat in the innervated group. Responses in the denervated group were not significantly different from those in the innervated group. The degree of the inotropic response was positively correlated with the magnitude of the increase in heart rate (r = 0.91). The decay in augmented contractility after decreasing the rate back to control levels fits an exponential relationship with a mean t((1/2)) of 1.7 s. Thus, in conscious man, increases in heart rate represent a positive inotropic stimulus, independent of other factors influencing ventricular performance and unaffected by neural innervation, and should be considered when changes in cardiac function are interpreted during serial studies or after drug administration.

Nonhypoxemic hazards of prolonged myoclonus.

Hyperkalemia, hyperthermia, and systemic hypotension developed in a patient with generalized myoclonus. These disorders reached life-threatening proportions but were rapidly and completely corrected after the patient was paralyzed with pharmacologic agents. Induced neuromuscular blockade may be indicated when the systemic effects of pathologically contracting muscle become life-threatening.

Validity of left-ventricular ejection fractions measured at rest and peak exercise by equilibrium radionuclide angiography using short acquisition times.

To validate ejection fraction (EF) calculations from 5 and 2 minutes of multiple-gated equilibrium radionuclide angiographic data and to establish its utility during alterations in cardiac performance, we studied 38 patients with chest pain suggestive of coronary artery disease. Twenty-four patients underwent contrast ventriculography (CV) as well as first-pass (FP) and equilibrium (EQ) radionuclide angiography at rest, and 14 additional patients had both radionuclide tests performed at rest as well as during peak supine bicycle exercise. The resting 5-min acquisition ejection fractions were compared between each method and the following correlations were generated: r = .92, n = 24 (CV-EQ), r = .92, n = 24 (CV-FP), and r = .95, n = 38 (FP-EQ). The variability of EQ-EF calculations between two independent observers was less than 2%; the mean absolute difference between two sequential 2-min acquisitions and the 5-min recordings was -.1 +/- 1.6%, and the reproducibility of sequential 2-min ejection fractions was excellent (r = .98). EQ and FP ejection fractions at symptom-limited exercise correlated well (r = .96, n = 14). We conclude that equilibrium radionuclide angiography is a valid method to measure EF both at rest as well as during peak exercise even when 2-min acquisition periods are used.

Altered adrenergic activity in coronary arterial spasm: insight into mechanism based on study of coronary hemodynamics and the electrocardiogram.

To elucidate the pathophysiologic mechanism of coronary arterial spasm, the hypothesis was examined that underlying alterations in sympathetic activity may account for this syndrome in some patients. Observations were directed to alterations in coronary arterial hemodynamics and the electrocardiogram. Spasm of the left anterior descending coronary artery produced a mean increase in coronary vascular resistance of 107 percent (P less than 0.05) in four patients in whom coronary sinus blood flow was measured with the thermodilution technique. The alpha adrenergic blocking agent phentolamine, given intravenously, acutely reversed coronary spasm and its clinical manifestations in eight patients and reduced coronary resistance. In four patients, administration of the long-acting oral alpha blocking agent phenoxybenzamine (20 to 80 mg/day) caused disappearance of symptoms during a follow-up period of 3 to 12 months. Transient prolongation of the corrected Q-T interval preceded spontaneous or ergonovine maleate-provoked coronary spasm in 11 patients with variant angina pectoris, whereas no significant change in the Q-T interval followed ergonovine administration in 27 control patients with atypical chest pain who did not have coronary spasm. T wave inversions in the resting electrocardiogram were normalized by isoproterenol infusion in one patient and by long-term phenoxybenzamine treatment in four patients with variant angina pectoris. These Q-T and T wave changes are analogous to those described with unilateral or asymmetric stellate ganglion stimulation in animals. These observations suggest that alterations in the sympathetic nervous system that are consistent with asymmetric stellate ganglion activity and transient alpha adrenergic receptor stimulation can presage the development of coronary arterial spasm in some patients with variant angina pectoris.

Coronary hemodynamic effects of ergonovine maleate in human subjects.

The coronary hemodynamic effects of ergonovine maleate were examined in 15 patients with a chest pain syndrome not thought to be variant angina. Ergonovine was given intravenously in sequential doses of 0.05, 0.1 and 0.25 mg while measurements were made of systemic hemodynamic variables, coronary sinus blood flow and coronary arteriovenous oxygen difference at intervals during the protocol. Coronary arterial diameters were measured from the 35 mm cineangiogram. Despite an increase in myocardial metabolic demand, as estimated with the heart-rate-blood pressure product, there was no apparent increase in coronary vascular resistance. In addition, there was a significant widening of the coronary arteriovenous oxygen difference in five of the seven patients in whom it could be measured. However, neither chest pain nor ischemic electrocardiographic changes were evoked. Although ergonovine also produced a diminution in epicardial coronary arterial diameters, this effect was not sufficient to explain the absence of appropriate coronary vasodilation. These results suggest that ergonovine may limit the normal vasodilatory response of the arteriolar bed to increases in myocardial metabolic demand.

Recurrent tachyarrhythmia associated with a bifocal demand pacemaker.

A recurrent tachyarrhythmia complicated the course of a patient with a permanent atrioventricular sequential (bifocal) demand pacemaker. Investigation by intracardiac electrocardiographic studies revealed that the arrhythmia was associated with normally functioning bifocal pacemaker, whose atrioventricular sequential interval approximated the patient's conduction time from atrium to ventricle. The mechanism of initiation and conversion of the arrhythmia was elucidated. Appreciation of this arrhythmia is necessary for appropriate clinical use of a bifocal demand pacemaker.

Early and intermediate term clinical outcome after multiple coronary stenting.

OBJECTIVE: To examine the immediate and intermediate term clinical outcome of multiple coronary stenting. DESIGN: Consecutive patients were prospectively entered on a dedicated database. Follow up information was obtained from outpatient and telephone interviews with patients and family physicians. SETTING: A tertiary referral centre. PATIENTS: 140 consecutive patients underwent multiple coronary stenting between April 1994 and November 1996. Most patients had unstable coronary syndromes. MAIN OUTCOME MEASURES: Death, cerebrovascular accidents, myocardial infarction (MI), coronary artery bypass surgery (CABG), and repeat angioplasty (PTCA). RESULTS: The angiographic success rate was 100% and the clinical procedural success rate 93%. The mean (SD) follow up was 11.9 (7.2) months (range 2-32). The mean (SD) number of stents per patient was 2.4 (0.7). The mean (SD) number of lesions treated per patient was 1.4 (0.6). There were four in-hospital deaths (2.9%) and five patients (3.6%) had an MI before hospital discharge. All in-hospital deaths occurred in patients presenting with an acute MI and cardiogenic shock. Three patients (2.2%) had a late MI. One patient with stent thrombosis underwent emergency CABG. Three patients (2.2%) underwent late CABG. Eight patients (5.7%) had a repeat PTCA. Eighty three patients (61.5%) were asymptomatic at follow up and 121 (86.4%) were free from major clinical events. CONCLUSION: In an era of increased operator experience, high pressure stent deployment, and reduced anticoagulation with antiplatelet treatment alone, multiple coronary stenting may be performed with a high procedural success rate and good intermediate term outcome.

Preliminary experience at a Canadian centre with directional coronary atherectomy for complex lesions.

OBJECTIVE: To evaluate preliminary experience of directional coronary atherectomy for complex coronary artery lesions. DESIGN: Nonrandomized, sequential patients with coronary arterial lesions that were ostial, eccentric, bulky, recurrent or membranous. SETTING: Cardiac catheterization laboratory of a tertiary referral general hospital. PATIENTS: Twenty-three patients with angina pectoris refractory to medical therapy who were suitable candidates for coronary bypass surgery. INTERVENTIONS: Directional coronary atherectomy with associated balloon angioplasty, if required, to reduce lesion stenosis to less than 25%. MAIN RESULTS: Primary success was achieved in 29 of 33 lesions (88%) by atherectomy alone and in 31 of 33 lesions (94%) by additional use of balloon angioplasty. Atherectomy retrieved tissue in 30 of 33 attempts (91%). One patient suffered Q wave myocardial infarction; one had acute occlusion after atherectomy requiring emergency balloon angioplasty; and one required repair of a false aneurysm of the femoral artery. CONCLUSIONS: Directional coronary atherectomy is safe and efficacious for ostial, bulky and eccentric lesions not optimally suited to balloon angioplasty. Lesions which have tortuous segments immediately beyond, restricting movement of the stiff nose-cone, and which are membranous or bandlike, may not be indicated for directional coronary atherectomy.

Antiplatelet therapy alone is safe and effective after coronary stenting: observations of a transition in practice.

OBJECTIVE: To evaluate the safety and efficacy of transition in practice after coronary stenting to antiplatelet therapy alone compared with anticoagulation with warfarin. DESIGN: Retrospective analysis of coronary stent management in a tertiary Canadian centre. PATIENTS: A total of 136 consecutive patients (146 lesions) were analyzed who underwent Palmaz-Schatz coronary stenting over a 15-month period and were treated with anticoagulation with warfarin (56 patients) or antiplatelet therapy alone with ticlopidine and acetylsalicylic acid (80 patients) during the transition in poststenting therapy in the authors' practice. Treatment was continued for 30 days in both groups. High pressure stent deployment was used in the majority of cases (greater than 90%), and use of intravascular ultrasound was infrequent (less than 12%). MAIN RESULTS: At 30 days, there were no clinical manifestations of stent thrombosis, coronary artery bypass surgery or repeat angioplasty in either group. One death occurred in the antiplatelet group. Periprocedural non-Q wave myocardial infarction occurred in two patients in the antiplatelet group and in one patient in the warfarin group. There was a significantly higher incidence of vascular complications in the warfarin group than in the antiplatelet group (14.3% versus 2.5%, respectively, P = 0.04). The length of hospital stay was significantly shorter in the antiplatelet group than in the warfarin group (3.0 +/- 1.8 versus 6.7 +/- 2.6 days, respectively, P < 0.001). CONCLUSIONS: Reduced anticoagulation with antiplatelet therapy alone after coronary stenting, despite infrequent use of intravascular ultrasound, is an effective and safe strategy with a low rate of vascular complications, a relatively short hospital stay and a low incidence of clinical manifestations of stent thrombosis.

Clinical outcomes of patients more than one year following randomization in the Canadian Coronary Atherectomy Trial (CCAT).

BACKGROUND: The Canadian Coronary Atherectomy Trial (CCAT) assessed, in a randomized comparison, the clinical and angiographic outcomes following atherectomy with those following balloon angioplasty for the treatment of de novo lesions in the proximal one-third of the left anterior descending artery (LAD). Although the procedural success rate was somewhat higher and the postprocedure lumen larger in patients treated with atherectomy, lumen dimensions, restenosis rates and clinical outcomes were similar in the two groups at six months. To determine whether late differences emerged between the groups, clinical follow-up was obtained at a median of 18 (range 10 to 31) months after randomization. METHODS AND RESULTS: Patients were contacted monthly by telephone for the first six months. Subsequent follow-up information was obtained in 272 (99%) of the 274 randomized patients via a clinic visit or telephone interview with the patient and/or a relative. Additional information was obtained from the referring physician as required. There were no differences in adverse events between the two groups during follow-up. In patients randomized to atherectomy compared with balloon angioplasty, death occurred in 1.5% versus 2.2% (cardiac death 0.7% versus 0.7%); myocardial infarction in 5.1% versus 5.9% (Q wave 1.5% versus 1.5%); coronary bypass surgery in 13.1% versus 12.6%; and repeat target lesion intervention in 22.6% versus 21.5%. Persistent or recurrent Canadian Cardiovascular Society class III/IV angina not treated by a further intervention was present in 1.5% versus 2.2%. The combined end-point of death or nonfatal myocardial infarction occurred in nine (6.6%) versus 11 (8.1%) patients and any adverse cardiac event in 50 (36.5%) versus 53 (39.3%). Multivariate logistic regression indicated that unstable angina, reference vessel size and preprocedure minimum lumen diameter were the only variables independently associated with adverse events. CONCLUSIONS: The initial choice of directional atherectomy or balloon angioplasty had no impact on clinical outcome over a period of 18 months in this patient population. With either technique, just over 60% of patients with proximal LAD disease experienced sustained symptomatic improvement without an adverse event following a single procedure, and 80% achieved this status following a repeat percutaneous intervention.

Double Marker ACX II: a new balloon catheter for coronary stent delivery.

We report our initial experience using the Double Marker ACX II for intracoronary stent deployment in 22 patients, 10 of whom were elective stents and 12 of whom were stented for complications following failed coronary angioplasty. The overall success rate was 95 percent. This dilatation catheter offers advantages which include accurate stent deployment with a double marker system, the option of using a delivery sheath, and the ability to deliver multiple stents with the same balloon catheter.

Balloon embolization of latrogenic aortocoronary arteriovenous fistula.

A detachable latex balloon was used to occlude an iatrogenic aortocoronary arterio-venous fistula. The aim of providing retrograde myocardial perfusion was not achieved to any significant degree because of rapid recruitment of collateral venous routes to the coronary sinus. This may have implications for the effectiveness of deliberate grafting of the coronary venous system with proximal venous ligation, as has been recommended when the coronary arterial system is small and diffusely diseased.

Pulmonary hypertension associated with primary biliary cirrhosis in the absence of portal hypertension: a case report.

Pulmonary hypertension is well described in association with portal hypertension of any cause including end stage primary biliary cirrhosis (PBC). The essential feature of this association is the presence of portosystemic shunting, including surgically created shunts. A patient with primary pulmonary hypertension and PBC without portal hypertension is reported. This suggests that primary pulmonary hypertension may be associated with PBC in the absence of portal hypertension. Decisions regarding appropriate organ transplantation may depend on whether pulmonary hypertension is primary or secondary to portal hypertension.

Depressant effect of digoxin on atrioventricular conduction in man.

We examined the effect of chronically administered digoxin on atrioventricular (A-V) conduction in nine cardiac transplant recipients. We assessed A-V conduction by measuring the duration from the pacing stimulus to the onset of the QRS complex (S'R interval) and by determining the occurrence of Wenckebach periodicity during rapid atrial pacing. We made measurements during a control period and during a period of digoxin administration of up to 37 days. During the digoxin period, the cycle length at which Wenckebach block occurred was prolonged by 14% of the control value and the S'R interval was significantly prolonged at paced rates of 110 beats per minute and faster. After digoxin was discontinued, the Wenckebach periodicity and S'R interval returned to control values. Atropine and propranolol did not alter digoxin's effect on A-V conduction. We conclude that digoxin exerts a direct (or non-neurally mediated) depressant effect upon A-V conduction in man, although the stress of tachycardia is necessary to demonstrate the effect.

Reduction of coronary blood flow during coronary artery spasm occurring spontaneously and after provocation by ergonovine maleate.

A 50-year-old man suffering from recurrent chest pain accompanied by transient ST-segment elevation developed spasm of the left anterior descending coronary artery after receiving ergonovine maleate. During spontaneous chest pain, thermodilution coronary sinus blood flow fell from 96 ml/min to 46 ml/min, while the coronary sinsu arteriovenous oxygen difference widened from 9.82 volumes percent to 11.3 volumes percent. During spontaneous relief of pain, coincident with resolution of the ST-segment changes, coronary sinus blood flow gradually rose to 135 ml/min, while coronary sinus arteriovenous oxygen difference narrowed to 6.82 volumes percent. Similar aterations in coronoary sinus blood flow accompanied chest pain provoked by ergonovine maleate. A thallium-201 scan confirmed a perfusion defect in the distribution the left anterior descending coronary artery. Thus, coronary artery spasm can produce a marked deficity in coronary blood flow that is associated with increased myocardial oxygen extraction; release of spasm creates a hyperemic response.