Adult Congenital Heart Disease

What Adult Congenital Cardiology Fellows Actually Do

Adult congenital heart disease (ACHD) fellowship prepares cardiologists to manage the growing, aging population of patients who survived surgically or catheter-palliated congenital heart disease into adulthood. That population now exceeds the number of children with CHD in the United States, and its complexity compounds with age: prior Fontan circulations developing protein-losing enteropathy, repaired tetralogy of Fallot presenting with late right ventricular failure, baffled transpositions reaching their fourth decade with systemic ventricular dysfunction.

A typical ACHD fellow's week spans several distinct domains simultaneously:

Longitudinal outpatient clinic: The volume and cognitive core of the practice. Fellows manage arrhythmia surveillance, ventricular function monitoring, endocarditis prophylaxis decisions, and the slow accumulation of hemodynamic changes that require intervention planning over years, not hours.
Diagnostic imaging interpretation: ACHD requires functional competence in echocardiography (transthoracic and transesophageal, with congenital-specific windows), cardiac MRI, and cardiac CT. Segmental anatomy and three-dimensional spatial reasoning are not optional skills—they are the base language of the field.
Catheterization laboratory: Fellows participate in diagnostic and interventional catheterizations—device closures, pulmonary valve interventions, balloon dilation of stenotic conduits. Procedural exposure varies significantly by program; some programs produce fellows with independent interventional competency, others orient toward diagnostic cath only. This is a critical question to ask before matching.
Inpatient consultation and co-management: ACHD fellows field consults for perioperative management of patients with CHD undergoing non-cardiac surgery, pregnancy management in high-risk anatomy, and acute decompensation in patients whose physiology does not behave like standard heart failure algorithms.
Multidisciplinary coordination: Every week involves active collaboration with congenital cardiac surgeons, cardiac anesthesiologists, maternal-fetal medicine specialists, electrophysiologists, hepatologists (for Fontan-associated liver disease), and pulmonologists managing pulmonary hypertension. The ACHD fellow is often the longitudinal quarterback across these services.

What is notably absent from most ACHD practices: the pure procedural rhythm of high-volume interventional cardiology, the protocol-driven management cadence of general cardiology, and the relative diagnostic clarity of single-organ disease. If those absences feel like losses rather than trades, that signal is worth examining before you commit to the path.

The ACHD Identity: Cardiologist, Internist, or Hybrid?

ACHD sits at an intersection that its own practitioners debate. Formally, the pathway runs through internal medicine and general cardiology. Clinically, the work demands fluency in congenital cardiac anatomy that feels closer to pediatric cardiology than to general adult cardiology. Socially and administratively, ACHD physicians are often embedded in adult hospitals that weren't originally designed for patients with repaired univentricular hearts.

This in-between position creates real professional tension for some fellows and real professional freedom for others. The tension: ACHD physicians are sometimes perceived as neither fully proceduralists nor fully internists, which can complicate identity within cardiology divisions that organize themselves by procedural volume and RVU productivity. The freedom: ACHD physicians often have more clinical autonomy, more longitudinal patient relationships, and more intellectual breadth than colleagues who specialize more narrowly.

The subspecialty has moved toward clearer self-definition. The American Board of Internal Medicine now certifies ACHD as a distinct subspecialty. The ACC/AHA have published dedicated ACHD competency and guideline documents. Dedicated ACHD programs at quaternary centers have enough patient volume and program structure to constitute a genuine intellectual community.

But the identity synthesis has to happen internally too. Fellows who thrive are those who have genuinely integrated the pediatric-origin anatomy, the adult-medicine comorbidity burden, and the longitudinal relationship model into a single clinical identity—not those waiting for the field to resolve into something tidier. If you need your subspecialty to have a clean lane and a clear procedural identity, ACHD will feel chronically ambiguous. If you find that ambiguity generative, you are probably in the right place.

Personality Traits That Thrive Here

Based on the consistent profile of clinicians who report high satisfaction in ACHD practice, several trait clusters predict fit:

Comfort with diagnostic complexity and incomplete information: ACHD patients frequently have anatomy that doesn't map onto standard guidelines. The evidence base is thinner than in general cardiology, the imaging is harder to interpret, and the hemodynamics behave unexpectedly. Physicians who find this intellectually stimulating rather than frustrating are well-suited. Physicians who become anxious without a clear algorithm will find ACHD chronically uncomfortable.
Longitudinal relationship orientation: Many ACHD patients have been in care since infancy. They know their anatomy better than many consultants. They have strong opinions about their management. They arrive with decades of medical history, prior surgical scars, and in some cases trauma from earlier medical experiences. Building genuine, durable therapeutic relationships—and finding that work meaningful rather than burdensome—is close to a prerequisite for satisfaction in this field.
Intellectual breadth tolerance: A single ACHD clinic day may require you to reason about pulmonary vascular resistance, fetal anatomy counseling, anticoagulation in Fontan circulation, arrhythmia management in surgically remodeled atria, and liver fibrosis staging. This is not a field that allows narrow optimization. Physicians who find broad engagement with complex physiology energizing will do well; those who prefer deep procedural mastery in one domain should examine whether that preference conflicts with what ACHD actually asks of you.
Multidisciplinary collaboration instinct: ACHD cannot be practiced in isolation. Physicians who find cross-disciplinary coordination rewarding—who are comfortable holding a longitudinal view while specialists manage individual components—thrive. Physicians who prefer autonomous decision-making with minimal input loops will find the coordination demands of ACHD friction-generating.
Emotional steadiness in chronic disease and loss: ACHD patients die younger than the general population. They face decisions about pregnancy that carry real maternal mortality risk. Some have progressive disease with no good surgical options. Clinicians who can hold that emotional weight without either detaching or burning through their reserve—and who have built deliberate practices for processing it—sustain long careers. This is discussed further in the burnout section below.

Traits That Struggle Here

Intellectual honesty requires mapping the mismatches as clearly as the fits:

Preference for procedural volume as primary professional identity: If your sense of competence and satisfaction is anchored in case volume, technical skill development, and procedural throughput, ACHD will under-deliver. Even programs with strong cath exposure do not produce proceduralists in the sense that structural cardiology or electrophysiology does. The cognitive work outweighs the procedural work in nearly every ACHD practice.
Discomfort with chronic illness management: Much of ACHD is watchful longitudinal management—monitoring for the expected deterioration, adjusting medications, deciding when the right moment for reintervention has arrived. If you find this style of medicine less engaging than acute management, or if you need frequent procedural or diagnostic resolution to feel effective, chronic disease continuity will feel unrewarding.
Strong need for algorithmic clarity: General cardiology has a dense evidence base and guideline architecture that supports structured decision-making. ACHD has guidelines, but for many specific anatomic lesions and clinical situations, the evidence is limited, expert opinion varies, and the cardiologist must reason from physiology rather than from protocol. Physicians who are uncomfortable with this degree of uncertainty—who need the guidelines to give them an answer—will find ACHD chronically unsettled.
Geographic inflexibility: This is not a trait issue but a structural reality that functions like one. ACHD practice is concentrated in a small number of academic quaternary centers. If your life constraints require you to practice in a specific geography without a major ACHD program, the career becomes very difficult to sustain. This should be assessed before fellowship, not after.
Compensation-driven subspecialty choice: ACHD compensation generally reflects academic medicine norms rather than high-volume procedural norms. If compensation is a primary driver of your subspecialty decision, adjacent tracks in structural cardiology or electrophysiology will likely produce higher productivity-linked earnings. That is not a criticism of ACHD—it reflects what the work is and who it attracts.

The Lifestyle Reality Check

ACHD fellowship and ACHD practice have a specific lifestyle profile that differs from other cardiology subspecialties in ways that are both advantages and constraints:

Call burden: Call in ACHD is typically lower volume than general cardiology or heart failure/transplant, and lower acuity than EP or interventional. Most ACHD calls involve clinical questions from internists managing admitted patients with CHD rather than catheterization lab activations. At major centers, there may be shared call arrangements with pediatric cardiology or general cardiology. That said, the cognitive complexity of those calls can be high—advising on a decompensating Fontan at 2 a.m. is not algorithmically simple even if the phone call volume is low.
Weekly schedule composition: A mature ACHD practice is predominantly outpatient clinic, with protected time for imaging interpretation, catheterization, and multidisciplinary conferences. Inpatient service time varies by program and faculty model. Compared to heart failure/transplant, ACHD typically involves less inpatient intensity and more outpatient continuity.
Geographic concentration: This warrants its own section below, but from a lifestyle standpoint, the practical implication is that geographic flexibility is low. You are likely to build your career in a major academic medical center city. If that aligns with your life, it is not a constraint. If it doesn't, plan accordingly before you commit to the subspecialty.
Academic versus community split: The overwhelming majority of ACHD practice is academic or quaternary-hospital affiliated. True community private practice in ACHD is rare—patient volume at any given community site is insufficient to sustain a full ACHD practice. Some physicians build hybrid models with satellite clinic arrangements at regional centers, but the core base is typically academic. This means academic medicine culture, academic medicine compensation structures, and academic medicine productivity expectations.
Research and education expectations: At most programs where ACHD jobs exist, some research or education activity is expected. Pure clinical ACHD positions without academic components exist but are uncommon. If you are averse to academic productivity expectations, audit this carefully when evaluating job offers.

Training Pathway and Timeline

The formal pathway to ACHD board certification runs as follows:

Internal medicine residency: Three years, ACGME-accredited. Standard IM training; ACHD-specific exposure at this stage is uncommon and not expected.
General cardiology fellowship: Three years, ACGME-accredited. Core cardiology training including echo, cath, nuclear, EP, and heart failure. Trainees who know they are heading toward ACHD should seek elective rotations in congenital cardiology during general fellowship, request mentorship from ACHD faculty, and if possible participate in ACHD clinic or catheterization. This exposure strengthens the ACHD fellowship application substantially and, more importantly, confirms fit before commitment.
ACHD fellowship: One year, following completion of general cardiology fellowship. Accredited programs must meet patient volume and case mix requirements established under the ACC/AHA ACHD training guidelines. Program size varies; some programs train one fellow per year, others two. The total number of accredited ACHD fellowship positions nationally is small relative to other cardiology subspecialties—this is a deliberately limited pipeline that reflects the patient population concentration.
Board certification: ABIM administers the ACHD certification examination. Eligibility requires completion of an accredited cardiology fellowship and an accredited ACHD fellowship. Candidates should verify current eligibility requirements with ABIM directly for their application year, as requirements are subject to revision.

Total timeline from start of IM residency to board-eligible ACHD cardiologist: a minimum of seven years of postgraduate training. This is a real commitment to quantify before starting the path.

A parallel pathway exists for pediatric cardiologists who complete additional ACHD training—this pathway has its own requirements and produces a distinct certification track. The page you are reading addresses the IM-based pathway. If you are coming from a pediatric cardiology background, verify current ABIM and ABPM dual-pathway requirements directly with the relevant boards.

What Strong Applicants Look Like

ACHD is a small field with a small fellowship applicant pool, which means the application is relationship-driven to a degree that exceeds most other cardiology subspecialties. Program directors know the training programs, know the faculty networks, and often know applicants through conference presentations, prior rotations, or shared mentors. This has implications for how to build an application:

Clinical performance in general cardiology fellowship: The most important signal. Strong fund of knowledge in cardiology broadly, demonstrated comfort with imaging interpretation, and positive evaluations from attending cardiologists—particularly those with CHD or structural cardiology expertise—carry significant weight. Fellowship programs communicate. A strong reputation from your general fellowship training is your most durable asset.
Prior CHD exposure: Documented rotations in congenital cardiology—pediatric or adult—during general fellowship are meaningful. They demonstrate intentionality and reduce training uncertainty for the ACHD program. If your general fellowship program has ACHD faculty, engage with them early. If it does not, pursue visiting rotations at programs with ACHD expertise.
Research productivity: Given the small evidence base in ACHD, there is genuine room for trainees to contribute original research even early in training. Case reports, registry contributions, and collaborative projects with ACHD faculty are all realistic during general fellowship. Research does not need to be in congenital cardiology specifically—structural cardiology, pulmonary hypertension, and cardiac imaging work is transferable. The signal is engagement with the intellectual culture of the field.
Mentorship network: ACHD is a field where being known by the right people matters more than in larger, less personal fields. Identify ACHD faculty at your training institution or nearby programs early in general fellowship. Attend the ACC's annual ACHD sessions and the specialized ACHD society meetings. Introduce yourself at those meetings; follow up on conversations. The field is small enough that genuine relationships are achievable and consequential.
Demonstrated commitment to the patient population: Program directors are evaluating whether you will stay in ACHD long enough to become good at it. A background in CHD that predates medical school—family experience, prior volunteer work, research exposure as a student—is relevant context. More important is being able to articulate specifically what draws you to this patient population and why that pull is durable rather than opportunistic.

The Burnout and Emotional Labor Profile

ACHD carries a specific emotional labor profile that is worth examining directly rather than eliding with generic wellness language.

The patients are not abstract cases. Many have known their diagnosis since childhood. They arrive with complex relationships with medical institutions, prior surgical trauma, anxiety about prognosis, and often a sophistication about their own physiology that exceeds many clinicians who encounter them for the first time. Building trust with this population requires sustained emotional investment that is both the work's greatest reward and its most significant drain.

Several ACHD-specific stressors deserve explicit acknowledgment:

Death in young adults: ACHD physicians lose patients who are in their twenties, thirties, and forties—patients with whom they have had longitudinal relationships, patients who have children, patients who have managed their disease with discipline and hope. This is categorically different from the expected deaths of elderly patients in other practices. The grief is real and should not be minimized or managed only with professional distance. Programs and practitioners who have named this and built collective structures for processing it sustain better than those that normalize it away.
Pregnancy counseling in high-risk anatomy: ACHD physicians counsel patients about pregnancies that carry materially elevated maternal risk—patients who want children, who may have planned their lives around the possibility. These conversations are among the most ethically and emotionally demanding in medicine. Fellows who have not encountered this work before training should seek it out early, evaluate their own capacity for it, and develop frameworks for holding patients through decisions with no good options.
Longitudinal disease progression without rescue: Some patients have anatomy that will progressively fail with no available intervention that changes the trajectory. The ACHD physician stays with those patients through that progression—adjusting comfort, managing complications, making referrals to palliative care—without the psychological exit of a procedural fix. This sustained witnessing is emotionally demanding work that requires deliberate attention to personal sustainability.
Patients who have outlived prognoses: Conversely, many ACHD patients have survived longer than their original surgical teams predicted. This creates a different kind of emotional complexity—patients who feel they are living on borrowed time, with its particular mix of gratitude, anxiety, and urgency. These relationships require more than clinical management; they require genuine human presence.

Clinicians who sustain long careers in ACHD typically share some combination of the following: deliberate peer support structures (often informal, within the small national community of ACHD physicians), protected time for reflection, explicit attention to the difference between empathic engagement and overidentification, and clear commitments outside medicine. None of these are unique to ACHD, but the specific emotional texture of this practice makes intentional cultivation of them non-optional rather than aspirational.

Comparing ACHD to Adjacent Fellowship Tracks

Four tracks are close enough to ACHD that applicants frequently compare them directly. The comparison is worth doing precisely, not impressionistically.

ACHD versus Structural Cardiology

Patient population: Structural cardiology focuses primarily on acquired valvular disease in older adults; ACHD focuses on congenital anomalies across the adult lifespan, with patients typically younger and carrying more surgical history.
Procedural scope: Structural cardiology is procedurally intensive—TAVR, MitraClip, TMVR, LAAO. ACHD has procedural components but is more cognitively than procedurally oriented. If procedural identity is important to you, structural cardiology has higher procedural density.
Career trajectory: Structural cardiology has expanded rapidly in academic and community settings, with more job opportunities and higher procedural compensation. ACHD career opportunities are more constrained geographically and institutionally.
Overlap: Both require sophisticated imaging. Both involve complex decision-making about intervention timing. Some ACHD patients require structural interventions managed collaboratively. These fields communicate, but they are distinct career paths.

ACHD versus Heart Failure and Transplant

Patient population: Heart failure/transplant manages advanced cardiomyopathy, primarily in older patients, with acute decompensation and mechanical support as core inpatient work. ACHD patients have structural rather than myopathic disease, are younger, and are managed more longitudinally than acutely.
Inpatient intensity: Heart failure/transplant is significantly more inpatient-intensive—VAD management, transplant evaluation and post-transplant care, acute hemodynamic crises. ACHD is predominantly outpatient. If you prefer hospital medicine cadence, HF/transplant reflects that; if you prefer the continuity model, ACHD does.
Emotional labor overlap: Both fields involve caring for patients with progressive disease and mortality that is not age-expected. The specific populations and clinical contexts differ, but both require the same emotional sustainability infrastructure.

ACHD versus Pediatric Cardiology

Training pathway: Pediatric cardiology runs through pediatrics residency and pediatric cardiology fellowship—a separate pipeline from IM-based ACHD. The two fields share patient anatomy but diverge in training, patient population management, and institutional home.
Patient age and context: Pediatric cardiologists manage neonates through adolescents; ACHD cardiologists manage the same patients after they transition to adult care. The overlap in anatomic knowledge is substantial; the clinical management context differs significantly—adult comorbidities, reproductive health, adult social determinants, and adult behavioral health enter the picture in ways that pediatric cardiology training does not fully prepare for.
Dual-trained practitioners: Some cardiologists complete training in both tracks and practice across the transition-of-care interface. This is a specialized career path with its own logistical and institutional requirements; it is not the standard pathway for either field.

ACHD versus Electrophysiology

Procedural identity: EP is one of the most procedurally intensive cardiology subspecialties. Ablation, device implantation, and lead management constitute a large share of the clinical week. ACHD has arrhythmia management as a core competency—arrhythmias are common in surgically repaired CHD—but ACHD physicians typically co-manage rather than independently perform complex electrophysiology procedures.
Career geography: EP jobs exist in academic and community settings broadly. ACHD jobs are geographically constrained. If geographic flexibility is a priority, EP is structurally more accommodating.
Cognitive profile: EP has its own diagnostic complexity but operates within a more procedurally structured framework than ACHD. The cognitive work is different in kind, not necessarily simpler.

Geographic and Job Market Realities

ACHD job geography is a structural fact that should be evaluated before fellowship, not after. The distribution of ACHD practice is driven by patient concentration: adults with complex CHD require quaternary-level support services—congenital cardiac surgery, advanced cardiac imaging, maternal-fetal medicine, specialized anesthesia—that exist at a limited number of institutions nationally. These tend to be major academic medical centers in large metropolitan areas.

What this means practically:

If you are geographically tied to a region that does not have a quaternary cardiac surgery program with ACHD infrastructure, a sustainable ACHD career in that region is unlikely. This is not a commentary on your competence; it is a reflection of where the patient infrastructure exists.
Academic medicine career structures dominate ACHD. The productivity metrics, promotion criteria, and compensation models of academic medicine apply. Physicians who prefer private practice autonomy will find the structural landscape of ACHD limiting.
Emerging satellite and hub-and-spoke models: Some major ACHD programs have developed regional clinic arrangements where ACHD faculty travel to affiliated community hospitals for periodic outpatient clinics. This extends geographic access for patients and creates some variation in where ACHD physicians spend their clinical time, but the primary institutional home remains the quaternary center.
Job openings in ACHD are infrequent by the standards of general cardiology. This is a feature, not a bug, of a small field: turnover is low because retention is high among practitioners who chose intentionally. But it means that timing, relationships, and geographic flexibility all matter more than in fields with high job turnover.
Fellowship program location matters beyond training: Fellows who train at a specific institution often have first-look access to faculty positions when they open, and build the relationships that lead to job offers at peer institutions. Where you do your ACHD fellowship influences where you will be able to practice, more than in larger fields with more distributed job markets. Evaluate fellowship programs with your long-term geographic preferences in mind.

Self-Assessment: Green Flags and Reconsideration Flags

The following indicators are grounded in what program directors and experienced ACHD physicians consistently identify as predictors of sustained fit and satisfaction. They are not a formula—they are prompts for honest self-examination.

You belong here if:

You find yourself more interested in understanding a patient's surgical history and hemodynamic trajectory than in the procedure you might eventually perform.
You have built strong longitudinal relationships with patients in prior training and found that continuity is among the most professionally rewarding aspects of medicine.
You are energized by cases where the textbook doesn't give you the answer and you have to reason from first principles.
You have experienced the ACHD patient population directly—through a rotation, an elective, or clinical exposure—and found it genuinely compelling rather than intellectually interesting in the abstract.
You can name specific anatomic lesions, describe their hemodynamic consequences, and articulate why the natural history of a repaired tetralogy differs from an unrepaired one. If you can't yet, you have a clear direction for your remaining general fellowship time.
You are willing to practice in an academic medical center, likely in a large city, for the foreseeable future.
You have thought seriously about the emotional demands of this patient population—young patients with progressive disease, pregnancy counseling with real mortality risk, loss in people your age—and arrived at a considered, not defensive, assessment of your capacity to sustain that work.
You are comfortable with limited evidence base and are prepared to be an active participant in generating the evidence rather than consuming it.

Reconsider carefully if:

Your primary draw to cardiology is procedural volume and technical mastery, and cognitive medicine feels like the consolation rather than the prize.
You have geographic constraints that conflict with the distribution of ACHD programs and jobs, and those constraints are not negotiable.
You find chronic disease management—the watching, adjusting, waiting, and longitudinal relationship maintenance—less professionally satisfying than acute care resolution.
You are choosing ACHD because it seems accessible rather than because the work itself calls to you. Small fields where access matters more than in large fields will not reward that logic—because program directors in small fields can detect it.
You have not had direct clinical exposure to ACHD patients and are reasoning entirely from abstract interest in CHD anatomy. Abstract interest in anatomy is insufficient evidence of fit with this specific clinical practice.

Questions to Ask Yourself Before Applying

These prompts are intended to surface values and constraints, not to produce reassuring answers. If a prompt produces genuine uncertainty, that uncertainty is useful information:

When I imagine my clinical practice in fifteen years, what fraction of it involves longitudinal outpatient relationships with patients I have known for years—and is that fraction exciting or depleting to contemplate?
Have I been in a room with an adult ACHD patient and their cardiologist, watched how those conversations actually run, and come away wanting to have that role—or did I find myself wanting something different?
Am I drawn to the intellectual complexity of ACHD, or to the identity of being rare and specialized? If the former, can I sustain that across years of managing the same anatomic variations; if the latter, is that a durable foundation for a career?
What is my plan if I match at an ACHD fellowship in City A and the job openings that emerge are in Cities B and C? Is my life structure compatible with that outcome?
Have I thought about the pregnancy counseling work specifically—sitting with a patient who has a systemic right ventricle and wants to carry a pregnancy, and walking through mortality risk estimates with her—and assessed my capacity for that conversation honestly?
How do I respond when I lose a patient who is my age or younger? Do I have structures—colleagues, rituals, practices—that allow me to process that without cumulative burnout? If not, am I prepared to build them?
Is my interest in ACHD specific to this patient population, or is it essentially an interest in complex structural cardiology that could be equally well served by structural cardiology or general cardiology at a high-complexity center?
Am I genuinely interested in contributing to the evidence base in congenital cardiology, or does academic medicine productivity feel like an obligation I will resent? ACHD practice without some research or education engagement is uncommon in the current job market.
What do I actually know about the non-cardiac complications of adult CHD—Fontan-associated liver disease, renal dysfunction from chronic low cardiac output, the neurological sequelae of cyanotic heart disease—and am I drawn to that complexity or indifferent to it?
If a mentor I deeply respected told me honestly that my temperament fit structural cardiology better than ACHD, would I be relieved, devastated, or genuinely uncertain? The answer tells you something about how resolved your fit actually is.

Next Steps If You're a Fit

If this page has clarified rather than complicated your direction, the following moves are concrete and time-sensitive:

Review the ACC/AHA ACHD guidelines and the ACC ACHD training competency documents. These are publicly available through the ACC website. They define what program-trained ACHD cardiologists are expected to know and do—reading them early tells you what general fellowship experiences to pursue and what knowledge gaps to close.
Identify ACHD faculty at your current training institution. If they exist, introduce yourself now, not in your final fellowship year. Ask about their patient population, their research, and whether you can participate in ACHD clinic or catheterization as an elective. The goal is both exposure and relationship-building.
If your program has no ACHD faculty, plan a visiting rotation. A month at a major ACHD program during general fellowship is achievable at most institutions with advance planning. It provides clinical exposure, tests fit in a real environment, and creates the relationship base that the application requires.
Attend ACHD-specific sessions at major cardiology meetings. The ACC Scientific Sessions includes ACHD content; the ACHD community also has focused society meetings. Attend, introduce yourself to fellows and junior faculty, follow up on conversations in writing. The community is small enough that presence is noted.
Identify a mentor who practices ACHD. This person should be someone who will give you honest feedback about your fit, not only encouragement. Ask them directly: "Do you think I'm suited for this, and what do I need to do differently?" A mentor who will say "I think structural cardiology fits you better" is more valuable than one who will only affirm.
Build your research contribution during general fellowship. Even a single case report or a contribution to an existing registry project demonstrates engagement with the field's evidence base. Identify a project early enough in general fellowship that it can be completed before you apply.
Review the PGY Zero cardiology subspecialty comparison pages for adjacent tracks—structural cardiology, heart failure and transplant, and electrophysiology—if you have not already. Understanding why ACHD is the right choice for you is easier and more credible when you have engaged seriously with the alternatives.