Emergency department use and hospital admissions among adult orthotopic heart transplant patients

Objective

To study the demographics, clinical presentations, and outcomes of emergency department (ED) visits of patients with heart transplantation (HT) in the United States.

Methods

We performed a secondary analysis of the National Emergency Department Sample database from 2016 to 2018. All ED visits of patients with HT aged ≥ 18 years were identified using International Classification of Diseases, Tenth Revision codes.

Results

Out of a total 308,182,495 national ED visits, 55,583 were HT‐related visits. The median age was 61.07 years (interquartile range [IQR]: 46.91–69.38) and 69.44% were males. The hospital admission rate was 54.3% and median inpatient length of stay was 3.19 days (IQR: 1.63–5.92). The mortality rate during inpatient stay was 1.16%. Median inpatient and ED charges among admitted patients were $37,911 (IQR: $21,487–$71,262). The most common primary diagnosis of HT‐related ED visits was sepsis (4.3%) followed by acute kidney injury (3.57%) and chest pain (3%).

Conclusion

More than half of total ED visits among HT patients resulted in hospital admission. The most common cause for ED visit in these patients was sepsis followed by acute kidney injury and chest pain.

Prognostic Role of Cardiopulmonary Exercise Testing in Wild-Type Transthyretin Amyloid Cardiomyopathy Patients Treated With Tafamidis

BACKGROUND

The prognostic value of cardiopulmonary exercise testing (CPET) in patients with wild-type transthyretin cardiac amyloidosis treated with tafamidis is unknown.

METHODS AND RESULTS

This retrospective study included patients with wtATTR who underwent baseline cardiopulmonary exercise testing and were treated with tafamidis from August 31, 2018, until March 31, 2020. Univariate logistic and multivariate cox-regression models were used to predict the occurrence of the primary outcome (composite of mortality, heart transplant, and palliative inotrope initiation). A total of 33 patients were included (median age 82 years, interquartile range [IQR] 79-84 years), 84% were Caucasians and 79% were males). Majority of patients had New York Heart Association functional class III disease at baseline (67%). The baseline median peak oxygen consumption (VO₂) and peak circulatory power (CP) were 11.35 mL/kg/min (IQR 8.5-14.2 mL/kg/min) and 1485.8 mm Hg/mL/min (IQR 988-2184 mm Hg/mL/min), respectively, the median ventilatory efficiency was 35.7 (IQR 31-41.2). After 1 year of follow-up, 11 patients experienced a primary end point. Upon multivariate analysis, the low peak VO₂ (hazard ratio [HR] 0.43, 95% confidence interval [CI] 0.23-0.79, P = .007], peak CP (HR 0.98, 95% CI 0.98-0.99, P = .02), peak oxygen pulse (HR 0.62, 95% CI 0.39-0.97, P = .03), and exercise duration of less than 5.5 minutes (HR 5.82, 95% CI 1.29-26.2, P = .02) were significantly associated with the primary outcome.

CONCLUSIONS

Tafamidis-treated patients with wtATTR who had baseline low peak VO₂, peak CP, peak O₂ pulse, and exercise duration of less than 5.5 minutes had worse outcomes.

A novel outpatient regimen in management of fluoropyrimidine-induced cardiotoxicity

e15613

Background: Fluoropyrimidines, such as 5-fluorouracil (5-FU) and capecitabine, are commonly used chemotherapies for solid tumors, and essential for curative intent treatment of colorectal cancer. But sometimes, their use may be limited by cardiac toxicity limiting the possibility of cure in some patients. Cardiotoxicity could be asymptomatic (EKG changes) or manifested as chest pain, arrhythmias, acute coronary syndrome or death. Rechallenging may be daunting and it may result in interruption or even discontinuation of planned chemo. Traditionally, nitrates and/or IV/oral calcium channel blockers (CCB) have been used for management of fluoropyrimidine-induced cardiotoxicity but without much benefit. Ranolazine, an oral antianginal drug approved for chronic angina, diminishes myocardial ischemia by reducing calcium overload caused by inhibition of late sodium current and it does not affect heart rate or blood pressure. Our objective was to evaluate the efficacy of our novel approach using ranolazine with other traditional drugs. Methods: 8 patients (median age 49.5 yrs) with fluoropyrimidine induced cardiotoxicity were retrospectively analyzed. They were rechallenged with the planned fluoropyrimidine regimen with our 3 drug cardioprotective regimen (KU protocol). This included oral Ranolazine 1000mg BID and Amlodipine 2.5 mg daily to start the day before starting 5FU infusion/oral capecitabine and to continue it until the day after completion of infusion/treatment, and Nitroglycerin paste 1 inch every 6 hours starting before infusion and continue until it was completed. These meds were discontinued upon completion of chemo. Results: 8 patients were rechallenged with fluoropyrimidine utilizing KU protocol, 6 patients (75%) were able to complete previously planned fluoropyrimidine regimen. One pt (*) discontinued capecitabine due to recurrent chest pain and treatment was switched to 5FU based regimen with KU protocol, which pt was able to complete without chest pain. Another pt (**), 5FU was stopped due to severe diarrhea, not due to cardiotoxicity. All pts tolerated KU protocol well. Conclusions: In our small, single center experience, we were able to safely and effectively rechallenge pts with fluoropyrimidines and complete curative intent treatment with our KU protocol. This protocol uses FDA approved oral and transcutaneous drugs without requiring a healthcare personnel to administer an IV CCB that can cause precipitous bradycardia and/or hypotension. Our results need validation in a larger cohort. [Table: see text]

Impact of Hormonal Therapies for Treatment of Hormone-Dependent Cancers (Breast and Prostate) on the Cardiovascular System: Effects and Modifications: A Scientific Statement From the American Heart Association

Cardiovascular disease and cancer are the leading causes of death in the United States, and hormone-dependent cancers (breast and prostate cancer) are the most common noncutaneous malignancies in women and men, respectively. The hormonal (endocrine-related) therapies that serve as a backbone for treatment of both cancers improve survival but also increase cardiovascular morbidity and mortality among survivors. This consensus statement describes the risks associated with specific hormonal therapies used to treat breast and prostate cancer and provides an evidence-based approach to prevent and detect adverse cardiovascular outcomes. Areas of uncertainty are highlighted, including the cardiovascular effects of different durations of hormonal therapy, the cardiovascular risks associated with combinations of newer generations of more intensive hormonal treatments, and the specific cardiovascular risks that affect individuals of various races/ethnicities. Finally, there is an emphasis on the use of a multidisciplinary approach to the implementation of lifestyle and pharmacological strategies for management and risk reduction both during and after active treatment.

Combined heart failure device diagnostics identify patients at higher risk of subsequent heart failure hospitalizations: results from PARTNERS HF (Program to Access and Review Trending Information and Evaluate Correlation to Symptoms in Patients With Heart Failure) study

OBJECTIVES

We sought to determine the utility of combined heart failure (HF) device diagnostic information to predict clinical deterioration of HF in patients with systolic left ventricular dysfunction.

BACKGROUND

Some implantable devices continuously monitor HF device diagnostic information, but data are limited on the ability of combined HF device diagnostics to predict HF events.

METHODS

The PARTNERS HF (Program to Access and Review Trending Information and Evaluate Correlation to Symptoms in Patients With Heart Failure) was a prospective, multicenter observational study in patients receiving cardiac resynchronization therapy (CRT) implantable cardioverter-defibrillators. HF events were independently adjudicated. A combined HF device diagnostic algorithm was developed on an independent dataset. The algorithm was considered positive if a patient had 2 of the following abnormal criteria during a 1-month period: long atrial fibrillation duration, rapid ventricular rate during atrial fibrillation, high (> or =60) fluid index, low patient activity, abnormal autonomics (high night heart rate or low heart rate variability), or notable device therapy (low CRT pacing or implantable cardioverter-defibrillator shocks), or if they only had a very high (> or =100) fluid index. We used univariate and multivariable analyses to determine predictors of subsequent HF events within a month.

RESULTS

We analyzed data from 694 CRT defibrillator patients who were followed for 11.7 +/- 2 months. Ninety patients had 141 adjudicated HF hospitalizations with pulmonary congestion at least 60 days after implantation. Patients with a positive combined HF device diagnostics had a 5.5-fold increased risk of HF hospitalization with pulmonary signs or symptoms within the next month (hazard ratio: 5.5, 95% confidence interval: 3.4 to 8.8, p < 0.0001), and the risk remained high after adjusting for clinical variables (hazard ratio: 4.8, 95% confidence interval: 2.9 to 8.1, p < 0.0001).

CONCLUSIONS

Monthly review of HF device diagnostic data identifies patients at a higher risk of HF hospitalizations within the subsequent month. (PARTNERS HF: Program to Access and Review Trending Information and Evaluate Correlation to Symptoms in Patients With Heart Failure; NCT00279955).

Lamin A/C mutation analysis in a cohort of 324 unrelated patients with idiopathic or familial dilated cardiomyopathy

BACKGROUND

Lamin A/C mutations are a well-established cause of dilated cardiomyopathy (DCM), although their frequency has not been examined in a large cohort of patients. We sought to examine the frequency of mutations in LMNA, the gene encoding lamin A/C, in patients with idiopathic (IDC) or familial dilated cardiomyopathy (FDC).

METHODS

Clinical cardiovascular data, family histories, and blood samples were collected from 324 unrelated IDC probands, of whom 187 had FDC. DNA samples were sequenced for nucleotide alterations in LMNA. Likely protein-altering mutations were followed up by evaluating additional family members, when possible.

RESULTS

We identified 18 protein-altering LMNA variants in 19 probands or 5.9% of all cases (7.5% of FDC; 3.6% of IDC). Of the 18 alterations, 11 were missense (one present in 2 kindreds), 3 were nonsense, 3 were insertion/deletions, and 1 was a splice site alteration. Conduction system disease and DCM were common in carriers of LMNA variants. Unexpectedly, in 6 of the 19 kindreds with a protein-altering LMNA variant (32%), at least one affected family member was negative for the LMNA variant.

CONCLUSIONS

Lamin A/C variants were observed with a frequency of 5.9% in probands with DCM. The novel observation of FDC pedigrees in which not all affected individuals carry the putative disease-causing LMNA mutation suggests that some protein-altering LMNA variants are not causative or that some proportion of FDC may be because of multiple causative factors. These findings warrant increased caution in FDC research and molecular diagnostics.

Thromboxane A2-induced arrhythmias in the anesthetized rabbit

Experiments were conducted in the anesthetized rabbit to investigate mechanisms for arrhythmias that occur after left atrial injection of the thromboxane A2 (TxA2) mimetic U-46619. Arrhythmias were primarily of ventricular origin, dose dependent in frequency, and TxA2 receptor mediated. The response was receptor specific since arrhythmias were absent after pretreatment with a specific TxA2 receptor antagonist (SQ-29548) and did not occur in response to another prostaglandin, PGF2α. Alterations in coronary blood flow were unlikely the cause of these arrhythmias because coronary blood flow (as measured with florescent microspheres) was unchanged after U-46619, and there were no observable changes in the ECG-ST segment. In addition, arrhythmias did not occur after administration of another vasoconstrictor (phenylephrine). The potential involvement of autonomic cardiac efferent nerves in these arrhythmias was also investigated because TxA2 has been shown to stimulate peripheral nerves. Pretreatment of animals with the β-adrenergic receptor antagonist propranolol did not reduce the frequency of these arrhythmias. Pretreatment with atropine or bilateral vagotomy resulted in an increased frequency of arrhythmias, suggesting that parasympathetic nerves may actually inhibit the arrhythmogenic activity of TxA2. These experiments demonstrate that left atrial injection of U-46619 elicits arrhythmias via a mechanism independent of a significant reduction in coronary blood flow or activation of the autonomic nervous system. It is possible that TxA2 may have a direct effect on the electrical activity of the heart in vivo, which provides significant implications for cardiac events where TxA2 is increased, e.g., after myocardial ischemia or administration of cyclooxygenase-2 inhibitors.

Omega-3 fatty acids in cardiac biopsies from heart transplantation patients: correlation with erythrocytes and response to supplementation

BACKGROUND

Omega-3 fatty acids (FAs) appear to reduce the risk of sudden death from myocardial infarction. This reduction is believed to occur via the incorporation of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) into the myocardium itself, altering the dynamics of sodium and calcium channel function. The extent of incorporation has not been determined in humans.

METHODS AND RESULTS

We first determined the correlation between red blood cell (RBC) and cardiac omega-3 FA levels in 20 heart transplant recipients. We then examined the effects of 6 months of omega-3 FA supplementation (1 g/d) on the FA composition of human cardiac and buccal tissue, RBCs, and plasma lipids in 25 other patients. Cardiac and RBC EPA+DHA levels were highly correlated (r=0.82, P<0.001). Supplementation increased EPA+DHA levels in cardiac tissue by 110%, in RBCs by 101%, in plasma by 139%, and in cheek cells by 73% (P<0.005 versus baseline for all; responses among tissues were not significantly different).

CONCLUSIONS

Although any of the tissues examined could serve as a surrogate for cardiac omega-3 FA content, RBC EPA+DHA was highly correlated with cardiac EPA+DHA; the RBC omega-3 response to supplementation was similar to that of the heart; RBCs are easily collected and analyzed; and they have a less variable FA composition than plasma. Therefore, RBC EPA+DHA (also called the Omega-3 Index) may be the preferred surrogate for cardiac omega-3 FA status.

Comparison of vasopeptidase inhibitor, omapatrilat, and lisinopril on exercise tolerance and morbidity in patients with heart failure: IMPRESS randomised trial

BACKGROUND

We aimed to assess in patients with congestive heart failure whether dual inhibition of neutral endopeptidase and angiotensin-converting enzyme (ACE) with the vasopeptidase inhibitor omapatrilat is better than ACE inhibition alone with lisinopril on functional capacity and clinical outcome.

METHODS

We did a prospective, randomised, double-blind, parallel trial of 573 patients with New York Heart Association (NYHA) class II-IV congestive heart failure, left-ventricular ejection fraction of 40% or less, and receiving an ACE inhibitor. Patients were randomly assigned omapatrilat at a daily target dose of 40 mg (n=289) or lisinopril at a daily target dose of 20 mg (n=284) for 24 weeks. The primary endpoint was improvement in maximum exercise treadmill test (ETT) at week 12. Secondary endpoints included death and comorbid events indicative of worsening heart failure.

FINDINGS

Week 12 ETT increased similarly in the omapatrilat and lisinopril groups (24 vs 31 s, p=0.45). The two drugs were fairly well tolerated, but there were fewer cardiovascular-system serious adverse events in the omapatrilat group than in the lisinopril group (20 [7%] vs 34 [12%], p=0.04). There was a suggestive trend in favour of omapatrilat on the combined endpoint of death or admission for worsening heart failure (p=0.052; hazard ratio 0.53 [95% CI 0.27-1.02]) and a significant benefit of omapatrilat in the composite of death, admission, or discontinuation of study treatment for worsening heart failure (p=0.035; 0.52 [0.28-0.96]). Omapatrilat improved NYHA class more than lisinopril in patients who had NYHA class III and IV (p=0.035), but not if patients with NYHA class II were included.

INTERPRETATION

Our findings suggest that omapatrilat could have some advantages over lisinopril in the treatment of patients with congestive heart failure. Thus use of vasopeptidase inhibitors could constitute a potentially important treatment for further improving the prognosis and well being of patients with this disorder.

Development and evaluation of the Kansas City Cardiomyopathy Questionnaire: a new health status measure for heart failure

OBJECTIVES

To create a valid, sensitive, disease-specific health status measure for patients with congestive heart failure (CHF).

BACKGROUND

Quantifying health status is becoming increasingly important for CHF. The Kansas City Cardiomyopathy Questionnaire (KCCQ) is a new, self-administered, 23-item questionnaire that quantifies physical limitations, symptoms, self-efficacy, social interference and quality of life.

METHODS

To establish the performance characteristics of the KCCQ, two distinct patient cohorts were recruited: 70 stable and 59 decompensated CHF patients with ejection fractions of <40. Upon entry into the study, patients were administered the KCCQ, the Minnesota Living with Heart Failure Questionnaire and the Short Form-36 (SF-36). Questionnaires were repeated three months later.

RESULTS

Convergent validity of each KCCQ domain was documented by comparison with available criterion standards (r = 0.46 to 0.74; p < 0.001 for all). Among those with stable CHF who remained stable by predefined criteria (n = 39), minimal changes in KCCQ domains were detected over three months of observation (mean change = 0.8 to 4.0 points, p = NS for all). In contrast, large changes in score were observed among patients whose decompensated CHF improved three months later (n = 39; mean change = 15.4 to 40.4 points, p < 0.01 for all). The sensitivity of the KCCQwas substantially greater than that of the Minnesota Living with Heart Failure and the SF-36 questionnaires.

CONCLUSIONS

The KCCQis a valid, reliable and responsive health status measure for patients with CHF and may serve as a clinically meaningful outcome in cardiovascular research, patient management and quality assessment.

An analysis of the effect of age on survival after heart transplant

BACKGROUND

Advances in immunosuppression and reports of improved survival after cardiac transplantation have led to a liberalization of traditional recipient eligibility criteria, especially age. While age alone is not a contraindication to transplantation, conflicting data exists regarding long-term survival of the older transplant recipient.

METHODS

One hundred-fifty three patients undergoing consecutive first time cardiac transplantation from June 7, 1985 through February 1, 1997 were studied. For purposes of analysis, patients were stratified according to age (<55 years vs. >55 years) and hospital and late outcomes determined.

RESULTS

The incidence of early and late acute cellular rejection was not different based up on age. The freedom from infection at 12 months was 54+/-5% for patients < or =55 compared to 32+/-8% for patients >55 years old (p = .04). Five year estimated survival for patients >55 years old was only 56+/-9% compared to 78+/-5% for patients < or =55 years old (p = .005). The hazard for death was highest within the first post-transplant year for older patients and was most commonly due to infection. Both advanced age and pre-transplant diagnosis of ischemic cardiomyopathy were found to be independently and additively predictive of reduced late survival.

CONCLUSIONS

In the present study, late survival was adversely influenced by advanced age. Older patients (>55 years) with pre-transplant diagnosis of ischemic cardiomyopathy were particularly at high risk (risk ratio 4.6:1) for death. Given little prospect of expanding the number of donor hearts, careful selection of patients over the age of 55 with pre-transplant ischemic cardiomyopathy is warranted.

Secular trends in cardiac transplant recipient and donor management in the United States, 1990 to 1994. A multi-institutional study. Cardiac Transplant Research Database Group

BACKGROUND

The growth of the US cardiac transplant waiting list has outpaced the increase in donors, resulting in a widening gap between the number of waiting recipients and available donors. These trends have generated concern that longer waiting times may result in more patients deteriorating to urgent status and that transplanting only patients who are in an advanced state of decompensation will reduce posttransplant survival. Furthermore, the shortage of donors may result in extending the guidelines for donor acceptability to a degree that increases graft failure and posttransplant mortality. We measured these secular trends in the Cardiac Transplant Research Database to provide current data on time-dependent changes in US cardiac transplant practice and survival.

METHODS AND RESULTS

At the time of this analysis, the Cardiac Transplant Research Database included all 2749 patients transplanted from January 1, 1990, to June 30, 1994, in the 25 participating transplant centers. During this 4.5-year period, the median waiting time for recipients who received a transplant increased from 2.7 to 3.5 months (P < .0001), and the proportion of recipients whose status was urgent at transplantation increased from 41% to 60% (P < .0001). Donor ischemic time increased from 150 to 166 minutes (P < .0001), and the proportion of donors requiring pressor support increased from 68% to 85% (P < .0001). Despite these changes in practice, the 1-year survival rate remained constant at 84% during this 4.5-year interval. There was no significant difference in 1-year survival rate between urgent status patients (83%) and nonurgent status patients (85%) (P = .08).

CONCLUSIONS

The widening gap between the number of waiting recipients and the number of donors has resulted in a continuing trend toward transplanting urgent status recipients and to a liberalization of donor acceptance criteria. Despite these changes, posttransplant survival has remained constant.

Diagnostic use of adenosine in two pediatric patients

We describe the successful diagnostic use of adenosine in two pediatric patients. In the first case, adenosine infusion enabled exclusion of accessory pathway conduction in a patient who had previous evidence of Wolff-Parkinson-White syndrome. In the second case, adenosine infusion aided in the diagnosis of a nonreciprocating reentrant atrial tachycardia in a postoperative Fontan patient. The transient atrioventricular nodal blocking effect of adenosine added diagnostic certainty which was not apparent from the surface 12-lead electrocardiograms or rhythm recording in both patients. As the therapeutic use of adenosine for reciprocating supraventricular tachycardia in children becomes more popular, clinicians should also recognize the situations in which its use may facilitate diagnosis of other supraventricular rhythms.

Matching the heart donor and heart transplant recipient. Clues for successful expansion of the donor pool: a multivariable, multiinstitutional report. The Cardiac Transplant Research Database Group

Little information is available regarding donor-specific parameters that predict success or failure after heart transplantation. Furthermore, with increasing numbers of patients awaiting heart transplantation, there is tremendous pressure to expand the donor pool by stretching the margins of donor acceptability. To gain insight into donor-related and donor-recipient interrelated predictors of death after transplantation, 1719 consecutive primary transplantations performed at 27 institutions between Jan. 1, 1990, and June 30, 1992, were analyzed. Mean follow-up of survivors was 13.9 months, and actuarial survival was 85% at 1 year. By multivariable analysis, risk factors for death included younger recipient age (p = 0.006), older recipient age (p = 0.0005), ventilator support at time of transplantation (p = 0.0006), higher pulmonary vascular resistance (p = 0.02), older donor age (p < 0.0001), smaller donor body surface area (female donor heart placed into larger male patient) (p = 0.003), greater donor inotropic support (p = 0.01), donor diabetes mellitus (p = 0.01), longer ischemic time (p = 0.0003), diffuse donor heart wall motion abnormalities by echocardiography (p = 0.06), and, for pediatric donors, death from causes other than closed head trauma (p = 0.02). The overall 30-day mortality rate was 7% but increased to 11% when donor age exceeded 50 years and was 12% when inotropic support exceeded 20 micrograms/kg/min dopamine plus dobutamine and 22% with diffuse echocardiographic wall motion abnormalities. The interaction of donor risk factors was such that the heart of a smaller female donor given high-dose inotropes placed into a larger male recipient produced a predicted 30-day mortality rate of 26% and the heart of a 25-year-old male donor given high-dose inotropes with diffuse echocardiographic wall motion abnormalities transplanted into a 50-year-old male recipient led to a predicted 30-day mortality rate of 17%. This analysis supports cautious extension of criteria for donor acceptance but with an anticipated greater risk in the presence of diffuse echocardiographic wall motion abnormalities and long anticipated ischemic time, particularly in older donors given inotropic support.

Sex-related differences in patients undergoing direct angioplasty for acute myocardial infarction

Important sex-related differences have been recognized in several coronary artery disease presentation and treatment subsets. Little data exist describing the relative findings and outcome in women versus men who received direct percutaneous transluminal coronary angioplasty for acute myocardial infarction. We studied 670 such patients of whom 464 (69%) were men and 206 were women. The women were significantly older (67 +/- 11 years vs 61 +/- 11, p < 0.001) but had undergone less prior coronary artery bypass graft surgery (6% vs 12%, p = 0.02), whereas prior myocardial infarction (17% women vs 22% men) and coronary artery disease distribution were not significantly different. Forty-one percent of women and 43% of men had single-vessel disease (p = NS). Both women and men had 1.5 lesions/patient dilated acutely, with similar success rates (95% women, 91% men; p = 0.08). Mean ejection fractions were similar (48% in both groups), and a similar percentage in each group had an ejection fraction < 30% (10% women vs 13% men). Over a mean follow-up period of 86 weeks, the need for repeat catheterization was frequent and was similar in both groups (44% women, 47% men; p = NS), whereas documented restenosis was less common in women (20% vs 28% of patients, p < 0.05). The need for coronary artery bypass grafting was similar (15% women, 17% men; p = NS), as was the need for repeat percutaneous transluminal coronary angioplasty in the infarct vessel (14% women, 18% men; p = NS) and overall mortality (7% women, 9% men; p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise echocardiography after coronary artery bypass grafting

Exercise echocardiography was used to assess the adequacy of regional myocardial perfusion in 125 patients who had undergone coronary artery bypass grafting. There were 108 men and 17 women (mean age 65 years) evaluated from 6 weeks to 16 years (mean 7 years) after surgery. Resting parasternal long- and short-axis and apical 4- and 2-chamber echocardiograms were recorded, digitized and stored. Maximal, symptom-limited upright treadmill exercise was then performed with continuous electrocardiographic monitoring. Repeat echocardiographic imaging and digitization were repeated within 1 minute of exercise termination. Resting and postexercise digitized echocardiograms were compared. A normal regional wall motion response to exercise consisted of improved segmental contraction and was used to predict uncompromised regional vascular supply. Unimproved or worsened segmental contraction after exercise was abnormal and was used as a predictor of regional vascular insufficiency. All patients underwent cardiac catheterization within 1 month after exercise testing. Regional coronary insufficiency was considered to exist when a segment's major vascular conduit exhibited greater than or equal to 50% luminal diameter reduction. Compared with the simultaneously acquired stress electrocardiogram, exercise echocardiography had superior sensitivity (98 vs 41%), specificity (92 vs 67%), positive predictive value (99 vs 91%), and negative predictive value (86 vs 12%) (p less than 0.001, 0.1, 0.01 and less than 0.001, respectively). In addition, exercise echocardiography correlated closely with the extent and regional distribution of compromised vascular supply. Exercise echocardiography is a highly sensitive, specific and accurate screening test for abnormal global and regional myocardial vascular supply in patients who have undergone coronary artery bypass grafting.

Histopathologic abnormalities of the sinus node compared with electrocardiographic evidence of sinus node dysfunction after the modified Fontan operation: an autopsy study of 14 cases

Autopsy specimens from 14 patients who had undergone a modified Fontan operation were evaluated to correlate the extent of histopathologic disruption of the sinus node with electrocardiographic findings of sinus node dysfunction. Patients with sinus node dysfunction (n=7) and those without (n=7) were similar in age, complexity of cardiac malformation, and number of postoperative days at time of death. The degree of fibrosis, local hemorrhage, necrosis, lymphocytic infiltration, and focal calcification of the sinus node and perinodal tissue was also similar in both groups. These findings, which showed a comparable amount of sinus node disruption in patients with normal sinus rhythm and in those with sinus node dysfunction, indicate a lack of correlation between the extent of histopathologic abnormality of the sinus node and electrocardiographic evidence of sinus node dysfunction.

Antitachycardia pacemaker treatment of postoperative arrhythmias in pediatric patients

An automatic antitachycardia pulse generator (Intertach 262-12) was implanted in each of six pediatric patients (mean age, 10 years) with drug-resistant and persistent postoperative supraventricular arrhythmias. Four had bradycardia-tachycardia syndrome, two after a Mustard procedure for transposition of the great arteries, one after a Senning procedure for the same anomaly, and one after a Fontan procedure for univentricular heart with transposition of the great arteries. Of the two remaining patients, one had atrial flutter after a modified Fontan procedure for univentricular heart and one had intra-atrial reentry tachycardia after a modified Fontan procedure for double-outlet right ventricle with pulmonary stenosis. During a mean follow-up interval of 31 months after implantation, pacemakers were activated on multiple occasions and functioned appropriately in all six patients. Complications necessitated six invasive interventions in three patients: erosion or infection of the system, adaptor fracture, and connector block fracture on one occasion each and lead dislodgment on three occasions. Four of the six patients continued to take drugs at the end of this study; however, all patients had their drug therapy reduced and one was taking digoxin only. The number of hospital admissions decreased after implantation. Despite a number of technical challenges, this newer multiprogrammable antitachycardia pacemaker appears to be a valuable addition to the treatment of refractory postoperative supraventricular tachyarrhythmias in pediatric patients.

Pseudo-preexcitation in tricuspid atresia

Because we have observed a relatively large number of tricuspid atresia patients with a short P-R interval and slurring of the initial QRS pattern suggesting preexcitation, we conducted a retrospective study to determine the frequency of this electrocardiographic pattern and whether or not this represented the presence of a true atrioventricular bypass tract. Three pediatric cardiologists reviewed the surface electrocardiograms of 183 consecutive tricuspid atresia patients who had been evaluated at the Mayo Clinic between 1980 and 1986. The patients' ages ranged from 4 months to 21 years; the male-to-female ratio was 5:4. The criteria for preexcitation included 1) a P-R segment <0.10 sec, 2) a QRS complex >0.10 sec, and 3) slurring of the upstroke of the QRS complex ("delta wave"). Of the 183 patients, 22 (12%) had P-R segments <0.10 sec, 9 of whom fulfilled the criteria for preexcitation. Five of these had a history of supraventricular tachycardia, and 4 of the 5 had undergone invasive electrophysiologic studies: 2 had enhanced atrioventricular-nodal conduction and 1 had normal atrioventricular-nodal conduction; only 1 had an accessory pathway. Our results indicate that, although many patients with tricuspid atresia meet the surface electrocardiographic criteria for preexcitation, many of these patients may not have an atrioventricular bypass tract; this state might be termed "pseudo-preexcitation." In these instances, invasive studies probably would not be necessary; regrettably, it may be difficult to distinguish between the presence and the absence of preexcitation in such patients without invasive electrophysiologic studies.

The use of percutaneous transluminal coronary angioplasty in myocardial infarction

To evaluate the effectiveness of percutaneous transluminal coronary angioplasty (PTCA) in the treatment of myocardial infarction, we reviewed the records of 508 consecutive patients treated within 6 hours of pain onset. Two hundred fifty-eight patients received direct PTCA without thrombolytic therapy, and 250 received thrombolytic therapy followed by immediate PTCA (within 24 hours, n=73) or delayed PTCA (later than 24 hours, n=177). The direct-PTCA group had the lowest initial success rate (92%) and the highest 1-week (8.1%) and 1-year (14%) mortality rates. Immediate PTCA had a 96% success rate, and 6.8% 1-week and 8.2% 1-year mortality rates. Delayed PTCA had the same initial success (96%), but lower 1-week (1.7%) and 1-year (2.3%) mortality. We conclude that both direct PTCA and combination treatment (thrombolytic therapy followed by PTCA) result in high rates of recanalizing occluded coronary arteries, but that combination treatment has higher initial success and survival rates, with delay in the use of PTCA producing the best survival rates.

The effects of hypoxemia on myocardial blood flow during exercise

We evaluated the adequacy of regional and transmural blood flow during exercise and rapid pacing after 1 wk of hypoxemia. Seven mature mongrel dogs were made hypoxemic (mean O2 saturation = 72.4%) by anastomosis of left pulmonary artery to left atrial appendage. Catheters were placed in the left atrium, right atrium, pulmonary artery, and aorta. Atrial and ventricular pacing wires were placed. An aortic flow probe was placed to measure cardiac output. Ten nonshunted dogs, similarly instrumented, served as controls. Recovery time was approximately 1 wk. Cardiac output, mean aortic pressure, and oxygen saturation were measured at rest, with ventricular pacing, atrial pacing, and with treadmill exercise. Ventricular and atrial pace and exercise were at a heart rate of 200. Right ventricular free wall, left ventricular free wall, and septal blood flow were measured with radionuclide-labeled microspheres. Cardiac output, left atrial blood pressure, and aortic blood pressure were similar between the two groups of dogs in all testing states. Myocardial blood flow was significantly higher in the right and left ventricular free wall in the hypoxemic animals during resting and exercise testing states. Myocardial oxygen delivery was similar between the two groups of animals. Pacing resulted in an increase in myocardial blood flow in the control animals but not the hypoxemic animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Cryosurgical modification of atrioventricular conduction for treatment of atrioventricular node reentrant tachycardia

Cryosurgical modification of atrioventricular (AV) node conduction was performed in five patients with AV node reentrant tachycardia that used dual AV nodal pathways and was refractory to drug therapy. The procedure alleviated the tachycardia in all patients without the development of complete heart block and without any associated surgical morbidity or mortality. These results suggest that cryosurgical modification of AV node conduction is a promising and potentially curative method of treating AV node reentrant tachycardia.

Results of the modified Fontan operation in adults

The results of the modified Fontan procedure were examined in 77 patients 18 years of age and older who underwent operation at this institution between October 1973 and December 1986. This series represents 16% of the patients undergoing the modified Fontan operation during that period. Of the 77 patients (46 men and 31 women), 29 had tricuspid atresia, 30 had double-inlet ventricle and 18 had other complex lesions. There were 5 (6%) hospital deaths, compared with 67 (17%) for patients of all ages undergoing the Fontan operation during the same period. Patient age 18 years and older was not a significant risk factor. There were 8 late deaths. Detailed follow-up data were available on 61 (95%) survivors from 5 months to 12 years (mean 4 years) postoperatively. Fifty-seven (93%) of the patients were in New York Heart Association class I or II, 20 (33%) were taking no medication and 11 (18%) were taking digoxin alone. Seventeen (28%) patients complained of persistent ascites or edema. The study indicated that (1) the modified Fontan operation can be performed with low mortality in adults, (2) the long-term outcome is favorable and (3) persistent ascites or edema may be a problem in some patients.

Plasma atrial peptide concentration during acute changes in cardiac filling pressure induced by a contrast agent

Left ventricular end-diastolic pressure and the concentration of atrial peptides in plasma were measured before and after the administration of contrast material into the left ventricle of 12 patients during cardiac catheterization. A positive relationship between changes in left ventricular end-diastolic pressure and the circulating level of atrial peptides was found in all 12 patients. Increases in plasma atrial peptide levels were detected within less than one minute after injection of the contrast agent. We conclude that the release of atrial peptides in the human is modulated rapidly by changes in atrial pressure. The rapid release of peptides from the atria in response to an increase in atrial pressure, coupled with evidence that atrial peptides reduce cardiac filling pressure, is consistent with the possibility that the atrial peptides may serve as part of a negative feedback system that enables the heart to influence its own filling pressure.

Clinical intracardiac electrophysiologic testing: technique, diagnostic indications, and therapeutic uses

Clinical cardiac electrophysiologic testing has evolved rapidly since 1968, when the technique was first described. In an electrophysiologic study, electrode catheters are positioned within the heart to record electrical activity from the atrium, atrioventricular conduction tissue, and ventricle. Programmed stimulation is then performed, which involves pacing of the atrium or ventricle and introducing critically timed premature stimuli during sinus rhythm or paced rhythm. The use of programmed stimulation in conjunction with intracardiac recordings in electrophysiologic studies has facilitated the diagnosis of mechanisms of arrhythmias and the assessment of therapy. Electrophysiologic testing is useful in selected patients with sinus node dysfunction, conduction system disorders, supraventricular tachycardia, ventricular tachycardia, or ventricular fibrillation and in survivors of out-of-hospital cardiac arrest and patients with symptomatic but unsubstantiated rhythm disturbances. Therapeutic approaches that can be assessed by electrophysiologic testing include serial drug testing to determine the effectiveness of antiarrhythmic agents, antitachycardia pacing, the implantable defibrillator, transcatheter ablation, and electrophysiologically guided surgical procedures. In this review, we discuss the methods of electrophysiologic testing, its clinical applications in diagnosing the various cardiac rhythm disturbances, and its use in assessing various therapeutic modalities.

Cardiac arrhythmias in patients with surgical repair of Ebstein's anomaly

Preoperative, perioperative and postoperative arrhythmias in 52 consecutive patients who underwent operation for Ebstein's anomaly were reviewed. There were 25 male and 27 female patients (mean age 18 years, range 11 months to 64 years). Thirty-four patients had one or more documented arrhythmias preoperatively (18 had paroxysmal supraventricular tachycardia, 10 had paroxysmal atrial fibrillation or flutter, 13 had ventricular arrhythmia and 3 had high grade atrioventricular block). Seven patients without documented arrhythmias had a history typical of tachyarrhythmias. During the perioperative and early postoperative periods, 14 patients had atrial tachyarrhythmias and 8 had ventricular tachycardia or ventricular fibrillation. There were seven deaths between day 1 and 27 months after operation. Five of these deaths were sudden (all in male patients, aged 12 to 34 years), and four of the patients had had perioperative ventricular tachycardia or ventricular fibrillation. One patient was taking one antiarrhythmic agent and another patient was taking two at the time of sudden death. Of the 18 patients with paroxysmal supraventricular tachycardia and 9 patients with paroxysmal atrial fibrillation or flutter preoperatively who were followed up for a mean of 40 and 36 months, respectively, 22 and 33% continued to have symptomatic tachycardia. Of the 11 patients (mean age 9 years) without preoperative documentation or symptoms of arrhythmia, follow-up data were obtained (range 1 to 144 months, mean 31) in 9 patients. None died suddenly or developed symptomatic arrhythmia.

Improved myocardial oxygen utilization by diltiazem in patients

Calcium entry blocking drugs produce different effects on systemic and coronary hemodynamics and myocardial oxygen extraction. To examine the effects on myocardial oxygen extraction, intravenous diltiazem (100 micrograms/kg bolus with a continuous 10 micrograms/kg/min infusion) was administered to 11 patients at rest and during controlled heart rates (100 +/- 5 and 120 +/- 5 bpm). At rest, diltiazem decreased mean arterial pressure from 109 +/- 13 to 99 +/- 14 mm Hg (p less than 0.01), increased heart rate from 64 + 12 to 74 +/- 14 bpm (p less than 0.01), and decreased coronary sinus resistance (1.02 +/- .41 to 0.87 +/- .40 U, p less than 0.05). Myocardial oxygen extraction was significantly reduced since coronary sinus oxygen content increased (6.0 +/- 0.9 to 7.8 +/- 1.2 ml/dl, p less than 0.01) and the arterial-coronary sinus oxygen difference decreased (12.0 +/- 1.7 to 10.6 +/- 1.6 ml/dl, p less than 0.01). Similar changes occurred with heart rate held constant. There were no significant changes in absolute coronary sinus blood flow, calculated myocardial oxygen consumption, or left ventricular dP/dt. Diltiazem decreases mean arterial pressure while reducing both myocardial oxygen extraction and coronary arterial resistance, suggesting that a principal mechanism of a beneficial effect upon the coronary circulation appears to be an improvement in myocardial oxygen extraction relative to myocardial oxygen demand.

Results of the modified Fontan operation for congenital heart lesions in patients without preoperative sinus rhythm

Preoperative sinus rhythm has been a criterion for the Fontan operation. However, of 297 patients who underwent the Fontan operation between October 1973 and February 1984, 12 (4%) did not have sinus rhythm. The age at operation ranged from 4 to 34 years (median 15). Nine patients had a univentricular heart, two had tricuspid atresia and one had a complex form of transposition. In all 12 patients, 3 to 8 of the 10 proposed criteria for operability were not met. An atrioventricular (AV) conduction abnormality was present in seven patients, six with complete AV block and one with AV dissociation. The patient with complex transposition had complete AV block and atrial fibrillation. Postoperatively, all seven patients continued to have an AV conduction abnormality, and those with complete AV block had a permanent pacemaker implanted. Six of the 12 study patients had atrial flutter or fibrillation refractory to antiarrhythmic medications. Postoperatively, four of the six patients had sinus rhythm. Two of the six patients had complete AV block (including the patient with complex transposition) and both had a permanent pacemaker implanted. Three of the 12 patients died (mortality rate 25%). The nine survivors were followed up for 6 to 55 months; no late deaths occurred. All had marked clinical improvement. This study demonstrates that 1) complete AV block is not a contraindication to the Fontan operation, 2) some patients may not require AV synchrony postoperatively for survival, and 3) postoperative atrial flutter or fibrillation may cease or be easier to control after the Fontan operation.

Surgical treatment of accessory atrioventricular pathways and symptomatic tachycardia in children and young adults

Twenty-seven patients aged 21 years or younger (mean 15) with symptomatic tachycardia underwent operation for ablation of an accessory atrioventricular pathway. Six patients had associated Ebstein's malformation of the tricuspid valve. Supraventricular tachycardia had been present for a mean of 5 years. At electrophysiologic study, 4 patients were found to have 2 accessory pathways. Left ventricular free wall pathways were found in 14 patients, right ventricular free wall pathways in 10 and septal pathways in 6. Successful initial ablation of all the pathways was achieved in 26 of the 27 patients. No patient died perioperatively and none had persistent complete heart block. During a mean follow-up of 11 months, no patient had recurrence of an arrhythmia related to the accessory pathway. Thus, the surgical treatment of children and young adults with accessory atrioventricular pathways and symptomatic supraventricular tachycardia is safe and effective. For these patients, unless the tachycardia can be easily controlled with a minimal number of drugs and adverse effects, surgical ablation should be considered early in the clinical course.

Regional coronary vasoconstriction after combined beta-adrenergic and calcium channel blockade in patients with coronary artery disease

The beta-adrenergic and calcium channel blocking drugs, which individually and combined have proven efficacious in the treatment of angina pectoris, appear to have opposing effects on coronary artery vasomotion. Previous studies have shown that beta-adrenergic blockade may potentiate and calcium channel blockade reverse coronary vasoconstriction during adrenergic cold stimulation in patients with coronary artery disease. To assess the coronary hemodynamic effects of combined drug therapy, thermodilution coronary sinus and great cardiac vein flow and mean arterial pressure were measured during serial cold pressor testing, both before and after 0.1 mg/kg of intravenous propranolol and again after the addition of 10 mg of sublingual nifedipine in 21 patients (9 without [group A1] and 12 with [group A2] greater than 50% narrowing of the left anterior descending coronary artery). In an additional 15 patients (6 patients without [group B1] and 9 with [group B2] left anterior descending artery stenosis), serial cold pressor testing was performed reversing the drug order. Despite significant increases in mean arterial pressure (p less than 0.01) during cold pressor testing, coronary sinus resistance responses after propranolol plus nifedipine were not statistically significant for any group. However, regional coronary resistance responses differed between patients with and without left anterior descending artery stenosis. In group A1, great cardiac vein resistance was unchanged after propranolol plus nifedipine. In group A2, great cardiac vein flow decreased significantly after propranolol plus nifedipine from 8 +/- 17 to -4 +/- 12% (p less than 0.01 versus control), and great cardiac vein resistance increased from 4 +/- 21 to 15 +/- 19% (p less than 0.01 versus control). A similar significant response was observed for groups B1 and B2. Regional coronary vasoconstriction during adrenergic stimulation after combined drug therapy was only observed in patients with significant left anterior descending artery stenosis. These data suggest that in some patients with severe coronary artery disease, combined beta-adrenergic and calcium channel blockade modified regional coronary responses to adrenergic stimulation with an inhomogeneous distribution of blood flow to potentially ischemic regions without affecting total coronary blood flow. These data also imply that an improvement in anginal symptoms after combined drug therapy may be due primarily to mechanisms that reduce myocardial oxygen demand rather than to improved myocardial oxygen supply.

Anterior pontic design: a logical progression

The fixed partial denture with multiple pontics can be enhanced by the elimination of embrasures between pontics while basic adherence to established design concepts is maintained. Continuing clinical observations are indicated.

Beneficial hemodynamic effects of intravenous and oral diltiazem in severe congestive heart failure

Concern persists about the potential negative inotropic effects of calcium channel blockers in patients with severely depressed myocardial function. Therefore, intravenous diltiazem (100 to 200 micrograms/kg per min infusion) was administered for 40 minutes followed by oral diltiazem (90 to 120 mg/8 hours) for 24 hours to patients with advanced congestive heart failure (New York Heart Association class III to IV, mean ejection fraction 26 +/- 4 [SD]). Intravenous diltiazem (eight patients) increased cardiac index 20% (2.05 +/- 0.8 to 2.47 +/- 0.8 liters/min per m2, p less than 0.01), stroke volume index 50% (22 +/- 9 to 33 +/- 12 ml/m2, p less than 0.001) and stroke work index 27% (19 +/- 10 to 24 +/- 10 g-m/m2, p less than 0.05); while reducing heart rate 23% (97 +/- 18 to 75 +/- 11 beats/min, p less than 0.01), mean arterial pressure 18% (95 +/- 13 to 78 +/- 7 mm Hg) and pulmonary wedge pressure 34% (29 +/- 9 to 19 +/- 7 mm Hg), without altering maximal first derivative of left ventricular pressure (dP/dtmax). Oral diltiazem (seven patients) produced equivalent hemodynamic effects. Transient junctional arrhythmias were observed in three of eight patients with intravenous diltiazem and one of seven patients with oral diltiazem. It is concluded that intravenous and short-term oral diltiazem improve left ventricular performance and reduce myocardial oxygen demand by heart rate and afterload reduction without significantly depressing contractile function in severe congestive heart failure. Caution should be exercised to avoid potential adverse, drug-induced electrophysiologic effects in such patients.

Differential effects of diltiazem and nitroprusside on left ventricular function in experimental chronic volume overload

To compare the hemodynamic effects of a calcium-channel blocker with those of a conventional vasodilator in the awake preinstrumented dog, diltiazem and nitroprusside were administered in equihypotensive infusions before (decrease in mean aortic pressure by 10%; p less than .001, n = 6) and after (decrease in mean aortic pressure by 12%; p less than .001) chronic volume overload (CVO) produced by an infrarenal aortocaval fistula. Diltiazem had no effect on preload either before or after CVO. The maximal rate of change in left ventricular pressure (dP/dtmax) was unaffected by diltiazem before the aortocaval fistula (decrease in dP/dtmax by 6%; p = NS) but was significantly reduced by calcium-channel blockade after CVO (decrease in dP/dtmax by 22%; p less than .001). By contrast, at matched aortic pressures nitroprusside significantly reduced left ventricular end-diastolic dimension (LVEDD) and pressure (LVEDP) in the same animals before (decrease in LVEDD by 10%, p less than .05; decrease in LVEDP by 7 +/- 2 mm Hg, p less than .001) and after CVO (decrease in LVEDD by 7%, p less than .05; decrease in LVEDP by 5 +/- 2 mm Hg, p less than .001) without altering dP/dtmax. We conclude that the calcium entry blocker diltiazem, unlike conventional vasodilators, may depress left ventricular function in CVO by direct negative inotropic properties in amounts that are without myocardial depressant effects in the presence of normal left ventricular performance.

Hypertrophic obstructive cardiomyopathy: hemodynamic improvement with intravenous verapamil

We report the reduction in left ventricular outflow tract gradient following the intravenous administration of verapamil to two pediatric patients with hypertrophic obstructive cardiomyopathy. Traditional therapy with beta adrenergic antagonists was relatively contraindicated in both patients. In a 15-year-old patient, the left ventricular outflow tract gradient decreased from 160 torr, at rest, to 45 torr during the verapamil infusion. In a 3-year-old boy, there was a reduction in the left ventricular outflow tract gradient from 60 torr, under basal conditions, to 10 torr during the intravenous verapamil infusion. We believe that verapamil may be effective in reducing the left ventricular outflow tract gradient in some pediatric patients with hypertrophic obstructive cardiomyopathy and may be useful in treating selected patients with this disorder.

Induction of ventricular tachycardia during electrophysiologic study after repair of tetralogy of Fallot

An association among premature ventricular complexes on routine electrocardiogram, elevated right ventricular systolic pressure and sudden death after repair of tetralogy of Fallot was previously reported. To examine this relation further, noninvasive, hemodynamic and invasive electrophysiologic data were studied in 27 patients who had undergone repair of tetralogy of Fallot 7 months to 21 years (mean 1.75 years) previously. Syncope, which had occurred in four patients, was not significantly related to ventricular arrhythmia on rest electrocardiogram, 24 hour electrocardiogram or treadmill test. All four patients with syncope had either nonsustained (two patients) or sustained (two patients) ventricular tachycardia induced at electrophysiologic study. His bundle to ventricle conduction interval was prolonged in two patients and Q to right ventricular apex interval was prolonged in three of the four patients. All four had abnormal anatomic or hemodynamic findings: two had a right ventricular systolic pressure of 70 mm Hg or more, one had right ventricular dysfunction with tricuspid insufficiency and one a septal aneurysm. The 9 patients with induced nonsustained or sustained ventricular tachycardia were then compared with the 15 patients without induced ventricular arrhythmias. Those with ventricular tachycardia had a greater prevalence of: more complex ventricular arrhythmia on 24 hour electrocardiogram (63 versus 0%, p less than 0.001), long His bundle to ventricle interval (44 versus 0%, p less than 0.001), right ventricular systolic pressure of 70 mm Hg or more (56 versus 0%, p less than 0.01) and reduced right ventricular ejection fraction (33 versus 7%, p less than 0.025). It is concluded that: 1) induction of nonsustained or sustained ventricular tachycardia was associated with a history of syncope; 2) all patients at risk for syncope could not be identified by routine electrocardiogram 24 hour electrocardiogram or treadmill test; 3) hemodynamic alterations may interact with intraventricular conduction abnormalities and predispose to ventricular tachycardia.

Symptomatic sick sinus syndrome in children and adolescents as the only manifestation of cardiac abnormality or associated with unoperated congenital heart disease

Sick sinus syndrome (SSS) occurs infrequently in children who have not undergone cardiac surgery. The symptoms, electrocardiograms, and electrophysiologic data in 11 patients aged 2 to 17 years who had nonsurgical SSS were reviewed. Syncope occurred in 5 patients and sinus bradycardia in 9. Sinus nodal recovery times were prolonged in 6 patients. The atrial effective refractory period was prolonged in 2 patients and the atrioventricular nodal functional or the effective refractory period, or both, was prolonged in 5 patients. Because patients with nonsurgical SSS may have abnormalities not only of the sinus node but also of the atrium and the atrioventricular node, it is recommended that patients with symptomatic SSS be evaluated by electrophysiologic study. The proper choice of antiarrhythmic drug therapy or permanent pacing procedure depends on a complete analysis of the cardiac conduction system.

Effect of ouabain on the anterograde effective refractory period of accessory atrioventricular connections in children

The anterograde effective refractory period of the accessory connection was determined before and after the administration of ouabain (0.015 mg/kg intravenously) during electrophysiologic studies in 21 patients with Wolff-Parkinson-White syndrome. The mean age (+/- standard deviation) was 10 +/- 2 years (range 1 month to 31 years). Each patient had stopped taking all cardiac drugs for more than 36 hours. Determination of the anterograde effective refractory period of the accessory connection was made using the atrial extrastimulus technique. A change in the anterograde refractory period of the accessory connection was defined as an increase or decrease of greater than 10 ms from the value before ouabain administration. The post-ouabain anterograde effective refractory period of the accessory connection increased in 2 (9%) of the 21 patients, decreased in 9 (43%) and was unchanged in 10 (48%). This study demonstrated a decrease in the anterograde effective refractory period of the accessory connection of 43% of patients with Wolff-Parkinson-White syndrome after the administration of ouabain.

Congenital complete atrioventricular block: clinical and electrophysiologic predictors of need for pacemaker insertion

Because of initial Adams-Stokes attack in the patient with congenital complete atrioventricular (A-V) block may sometimes prove fatal, there is a need to be able to identify the patient at great risk of having such attacks. Twenty-four children with congenital complete A-V block were followed up for 1 to 19 years to determine the efficacy of current methods of predicting risk for Adams-Stokes syncope and the usefulness of pacemaker therapy in relieving symptoms. The heart rate at rest, configuration of surface electrocardiographic complexes, data obtained during intracardiac electrophysiologic study and response to graded treadmill exercise testing were compared in children with and without syncope. One or more Adams-Stokes episodes were experienced by eight children, one of whom died. Only a persistent heart rate at rest of 50 beats/min or less demonstrated any significant (probability [p] less than 0.01) correlation with the incidence of syncope. Intracardiac electrophysiologic study was of little benefit because of site of block did not correlate with syncope. Although the increase in heart rate during treadmill exercise testing showed no correlation with prevalence of syncope or location of block, exercise-induced ventricular ectopic beats may have predictive value in older children and young adults. Ventricular pacemakers were implanted in 10 children. Each child was asymptomatic over a 1 to 10 year follow-up period. Because extreme bradycardia may contribute to the prevalence of Adams- Stokes attacks in children with congenital complete A-V block, careful evaluation of heart rate at rest may be an effective means of differentiating patients at risk of syncope. Pacemaker therapy is a feasible and effective method of treatment in young children and relieves symptoms