Does all global left ventricular (LV) hypokinesia mean dilated cardiomyopathy?

Global LV Hypokinesia vs. Dilated Cardiomyopathy

Not all global left ventricular hypokinesia indicates dilated cardiomyopathy, as LV systolic dysfunction can occur without ventricular dilation in conditions such as hypokinetic non-dilated cardiomyopathy (HNDC). 1, 2

Definition and Diagnostic Criteria

Dilated cardiomyopathy (DCM) is specifically defined by:

• Left ventricular or biventricular dilation
• Systolic dysfunction
• Absence of abnormal loading conditions (hypertension, valve disease)
• Absence of coronary artery disease sufficient to cause global systolic impairment 1

The key distinction is that DCM requires both ventricular dilation and systolic dysfunction, while global hypokinesia refers only to the systolic dysfunction component.

Hypokinetic Non-Dilated Cardiomyopathy (HNDC)

The European Society of Cardiology recognized HNDC as a distinct clinical entity in 2016, defined as:

• LV systolic dysfunction (reduced ejection fraction)
• Normal LV dimensions (no dilation)
• Absence of other causes such as coronary artery disease 2

HNDC may represent:

• An early stage of DCM that hasn't yet progressed to ventricular dilation
• A distinct cardiomyopathy phenotype with different pathophysiology
• A transitional phase in other cardiomyopathies 2

Clinical Differences Between HNDC and DCM

Research comparing HNDC and "classic" DCM has found:

1. Prevalence: More than 20% of patients with non-ischemic cardiomyopathy have HNDC without ventricular dilation 2

2. Clinical presentation:

   • HNDC patients have less severe heart failure symptoms
   • Lower NT-proBNP levels in HNDC
   • Lower diuretic requirements in HNDC
   • Less advanced cardiac remodeling in HNDC 2

3. Outcomes: Despite these differences, all-cause mortality and cardiovascular mortality are similar between HNDC and DCM patients 2

Other Causes of Global LV Hypokinesia Without Dilation

Global LV hypokinesia without dilation can also be seen in:

1. Early stages of other cardiomyopathies:

   • Early myocarditis
   • Early toxic cardiomyopathy (alcohol, chemotherapy)
   • Early tachycardia-induced cardiomyopathy 1

2. Transient conditions:

   • Stress-induced (Takotsubo) cardiomyopathy
   • Myocardial stunning after ischemia
   • Sepsis-induced cardiomyopathy 1

3. Left-dominant arrhythmogenic cardiomyopathy:

   • May present with global LV hypokinesia
   • Often has subepicardial fibrosis on CMR
   • Frequent arrhythmias 1

Diagnostic Approach

When global LV hypokinesia is detected:

1. Assess for ventricular dilation:

   • Echocardiography (first-line)
   • CMR for precise measurements 1

2. Exclude other causes:

   • Coronary artery disease (CT coronary angiography or invasive angiography)
   • Abnormal loading conditions (valve disease, hypertension)
   • Infiltrative diseases 1

3. Consider additional testing:

   • CMR for tissue characterization (fibrosis, inflammation)
   • Genetic testing if familial history
   • Endomyocardial biopsy if inflammation suspected 3

Clinical Implications

The distinction between global LV hypokinesia and DCM has important implications:

1. Prognostic: HNDC may have different natural history than DCM, though mortality appears similar 2

2. Therapeutic: Treatment approaches may differ based on the presence or absence of dilation

3. Familial screening: Important in both conditions if genetic etiology suspected 3

Conclusion

Global LV hypokinesia is a functional finding that can occur with or without ventricular dilation. While it is a key component of DCM, its presence alone is insufficient for a DCM diagnosis without concurrent ventricular dilation. The recognition of HNDC as a distinct entity highlights that global hypokinesia without dilation represents either a different cardiomyopathy phenotype or potentially an early stage in the DCM spectrum.